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RE: TTR250 - fitting a 325cc big-bore kit
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I love my 325. I had all the boring and honing done locally for a really great deal for ($100). The boring and honing was done to spec. And I ground the piston rings to appropriate clearances as well. Currently just finished braking in at 15 hours, with no smoke. And I apologize for not being able to accurately measure my thumper sleeve, as I only have a plastic caliper.

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Would you recommend the big-bore kit for someone considering overlanding to remote locations?

Extra horse power would be great for the open road and lugging big loads; but bullet proof reliability is needed too.

Also, do you know what the change in compression ratio is, if any?



-- Edited by Phil on Thursday 29th of November 2012 06:38:48 AM

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My credit card is groaning after picking up my 325 barrel from Hamlins - £187.20 was the damage. The overall cost of the rebuild also needs to take into account the cost of the new sleeve, piston rings and a gasket set.

Hamlin's bill covered pressing out the old sleeve, boring the barrel and pressing in (with Loctite) the new sleeve, shortening the new sleeve by 10cm (as Thumper Racing supplied one that was too long), chamfering the base of the barrel to take an O ring, boring the sleeve and gapping the new rings to fit.

The engineer was quite confident that this barrel is not going to develop cracks. The only marks I can see are vertical casting ones on one side only. The previous barrel had longitudinal cracks that allowed oil to weep out very slowly but messily.

The rebore was done to Wiseco specification this time. I mistakenly asked on the original rebore for extra clearance which resulted in the engine smoking on start up until the piston warmed and expanded.

The pic immediately below shows how much bigger the new sleeve is as the old sleeve fits inside it easily!

Barrel with new liner - old sleeve inside.jpg

 

Barrel with new liner 002.jpg

The pic below shows the casting marks I mentioned.

Barrel with new liner 001.jpg

 

Barrel with new liner 003.jpg

The pic below shows the chamfer. The engineer was restricted to a small chamfer as there was a risk of breaking through into the cavities. I now need to source an appropriate size O ring to suit.

Barrel with new liner - chamfer.jpg

 

Fingers crossed this rebuild holds up.

Brian



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Phil wrote:

Would you recommend the big-bore kit for someone considering overlanding to remote locations?

Extra horse power would be great for the open road and lugging big loads; but bullet proof reliability is needed too.

Also, do you know what the change in compression ratio is, if any?


Hi Phil.

I was hoping someone else may have responded to your question about overlanding a 325. I know that Robin Webb of Salt & Gold fame runs a 325 and I think he takes that over the dunes. 

I can't help with the new CR as I wasn't able to accurately measure the volume of the combustion chamber but my 325 runs fine with no overheating or pinking.

Brian



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I reckon the loctite should do the same job as the o-ring, in stopping capilliary action drawing oil up from the crankcase, but there's nowt wrong with belt and braces, and if that's how Mr Yamahasan designed it, it's probably right!

Been watching this thread for ages pondering investing time, effort and cash into this mod. There's now really only one question I'm struggling with before I go for it: 

Can Thumper really be relied upon to supply the right stuff? It seems multiple c$$$ups have occurred with wrong length and wrong diameter sleeves. With international shipping costs AND recommendations to let them do the work (so sending your own barrel out, or buying one on ebay-usa and getting it shipped straight to them - $$$), it all gets quite expensive if you're not guaranteed the right stuff, fitted right, first time. I get quite annoyed if I buy a pair of jeans on the web and they send the wrong size, so the thought of my baby being in bits for months, and the hassle of multiple phonecalls to Heathrow customs dept would probably push me over the edge!
Just asking

Simon.



-- Edited by mossproof on Monday 10th of December 2012 06:58:01 PM

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Hi Simon

I just lost a longish message so this one will be more succinct!

Despite the hassles, the 325 big-bore kit has transformed my TTR and I would do it all again - but in a better way.

Current Thumper price for the top end kit (using your barrel) is $615 (about £383) plus shipping. A s/h barrel would cost about £45 from eBay or elsewhere. Get the old liner pressed out before shipping it to Thumper and you will save some weight plus you will have a liner to sell. 

Wait until the finished article is back from the US and only then strip your motor out and get the crankcases opened up. Hamlins charged Chancey £55 for that work I recollect.

This is the way to do it if you don't want too much downtime on your TTR.

OK, the big bore route isn't cheap but, compared to what some of my mates spend on bling for their Katooms, it isn't out of the way and you end up with a nearly new engine that brings the TTR alive.

Having now been in the Totally TTRs business for a couple of years, I guess I have come to expect poor service from certain suppliers, eBay sellers, etc. and am getting hardened to it. It would drive me mad if I let it get to me! However, I still do get cross when poor service from one of my suppliers impacts on one of my customers evileye

Thumper Racing's communications aren't good if you go slightly off piste with them. Stick to their standard offering, or be prepared to use the phone, and you will be OK.

Can't wait to get my rebuilt engine back in the bike and check it out! If it all goes to plan then I will do the same for my "spare" 325 engine (the twin of mine) but, in the meantime, it is powering my TTR perfectly - albeit weeping a bit of oil wink

I hope that helps but can fully understand your concerns.

Brian



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It's been a while but I have actually now got my 325 engine back together with its new barrel and sleeve. I re-used the existing piston as it was pretty much in perfect condition but fitted new rings.

Delays caused by: Christmas and New year holidays and socialising with friends and family; looking after our grandsons (aged 3 and 4 years) for a week whilst their parents had a well-deserved holiday; a week's bout of the dreaded man flu'; and the search for a skinny O ring to fit in the newly machined groove at the base of the barrel (sourced an 84mm x 1.5mm O ring from a local supplier which arrived on Friday).

I have taken the tank, seat and side panels off the TTR and it has been power washed and ready for the engine transplant  - hopefully do it tomorrow if I can rope my brother into lifting duties biggrinbiggrin

I also have a genuine TTR oil cooler ready to fit just to give me a bit of extra oil capacity.

Onwards and upwards wink

Brian



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Slow progress today cry 

Despite having checked that the valve clearances were correct before lifting the head, I found that the exhaust valves were out of spec when everything was bolted up. This was to the extent that one of the valves wasn't closing completely and therefore no compression confuse

All fixed now but that was most of the morning gone.

Just a couple of tips that I have learnt from experience.

a) Wire the clutch actuator arm as it is too easy to get it the wrong side of the frame when putting the engine in - and you don't need that I promise you!

b) Tie the stator wires back out the way so the connector block doesn't get damaged.

c) When the engine is being worked on or power washed, I use a rubber "bung" in the inlet manifold. The bung is a petrol tank support from a metal tanked model and fits perfectly smile

325 engine rebuilt2.jpg



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My brother popped around yesterday afternoon and provided much needed motivation - plus a bit of muscle!

We soon had the old engine out and the rebuilt 325 engine fitted.

As usual with any job like this you get hiccups!

Firstly I noticed my drive chain had lost a roller - not bad after over 7,000 tough trail miles though (Renthal R3). However, I didn't want put on a new chain as there is still plenty of life left in the old sprockets (new chain needs new sprockets under my rules!) so I dug out a good spare only to find that it was too short with the 325's tall gearing. I added an extra link with a rivetted link on one side and a split link on the other (i.e. 2 extra links overall - you can only add links in pairs) to allow easy dismantling. Gotta say that I don't like rivet links. Might be OK with the right tool to peen over the head but I didn't like peening the rivet heads over on a vice using a ball peen hammer - seems very agricultural no  Anyways up, its on now and is doing the job.

Second hiccup was that my bro' managed to pull out an exhaust stud - doesn't know his own strength! Good job I keep an 8mm Helicoil kit handy. Trev had never fitted a Helicoil before so I let him do it as penance wink  The original stud was fine so I just cleaned it up and put it in with a bit of Loctite thread lock.

I put in 1,200ml of oil to start off with as I have no idea what the oil cooler holds. I took out the oil bleed bolt and the engine took quite a bit of turning over before oil came out. I think the newly fitted oil cooler probably has to be filled before the oil gets to the bleed hole.

Once the plug cap was put back on it started instantly and sounded fine. I let it warm up a bit to get the oil circulated and to check for obvious oil leaks. Moved it outside away from the carbon monoxide (cough cough!) and let the oil settle. I should have measured how much oil was needed to get up to level so that I know how much extra capacity I have from the cooler but I stupidly topped it up direct from the can - possibly another 200ml making about 1,400ml in total. If so, I am well pleased with that! 

Took it for a short break in run in the pouring rain and all is well. Parked it over somer clean cardboard and checked a couple of hours later and pleased to see no oil leaks biggrin

Now to put back the sump guard and side panels and do some serious miles to run it in. Hope the weather is better tomorrow.

Brian



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Good to hear that its up and running. what type of gearing are you running on your 325? I run 14-42. After a weekend in the dunes and 15miles of 2 foot deep whoops the clutch has started to slip in 6 gear pinned. my solution was to shim the clutch springs with washers(before the desert trip). I suspect the oil is contaminated and is aiding in the slipping.

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So far so good, eh? smile

Well done and here's hoping everything else goes as easily as this swap seems to have gone .  (Despite Tarzan Trout Tickler's strength biggrin)

A chain is only as strong as its weakest link. hmm

Martyn



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mingle wrote:

Good to hear that its up and running. what type of gearing are you running on your 325? I run 14-42. After a weekend in the dunes and 15miles of 2 foot deep whoops the clutch has started to slip in 6 gear pinned. my solution was to shim the clutch springs with washers(before the desert trip). I suspect the oil is contaminated and is aiding in the slipping.


 We have some quite technical going here so I run 14-45 or 46 although 14-44 would probably be OK. Will check tomorrow but I just used a good s/h sprocket I had in stock smile

Not surprised your clutch slipped after that sand. New friction plates are cheap enough though and will keep you going for a while longer if the washer trick doesn't do it wink

Brian



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Cubber wrote:

So far so good, eh? smile

Well done and here's hoping everything else goes as easily as this swap seems to have gone .  (Despite Tarzan Trout Tickler's strength biggrin)

A chain is only as strong as its weakest link. hmm

Martyn


 The weakest link will be hanging on to the handlebars Martyn biggrinbiggrinbiggrin



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TTRfan wrote:
mingle wrote:

Good to hear that its up and running. what type of gearing are you running on your 325? I run 14-42. After a weekend in the dunes and 15miles of 2 foot deep whoops the clutch has started to slip in 6 gear pinned. my solution was to shim the clutch springs with washers(before the desert trip). I suspect the oil is contaminated and is aiding in the slipping.


 We have some quite technical going here so I run 14-45 or 46 although 14-44 would probably be OK. Will check tomorrow but I just used a good s/h sprocket I had in stock smile

Not surprised your clutch slipped after that sand. New friction plates are cheap enough though and will keep you going for a while longer if the washer trick doesn't do it wink

 

 

The friction plates are new. could they be glazed?

 

Brian


 



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mingle wrote:
The friction plates are new. could they be glazed?

Hmmm - did you soak them overnight in oil before fitting? They don't like going in dry.....

Brian



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There seems to be quite a bit of interest in the Thumper big-bore kit so, for UK owners, here is a brief run down of costs:

Thumper 325 costs: 

Shipping your own (or a spare) barrel to the US - £20.00

Cost of Thumper supplying the full kit and installing their new oversize sleeve and piston in your barrel - £410.81

Return shipping to the UK - £40.08

Customs VAT & Parcel Force charge - £98.68

Boring out crankcases (locally) - £80.00 maximum - should be able to get it done closer to £60

Total £649.57

If you consider what other dirtbike owners spend on suspension mods, etc. for their bikes, I reckon this is good value for money to get a "WR killer" wink

There are additional costs if you refurb the crankshaft and fit new main bearings, etc. 

I recommend using Thumper to install the sleeve unless you have a local firm that you know are good, and used to working with small motorcycle engines. I recently had a new sleeve installed by a local firm (Hamlins of Bridgewater, Somerset) and they did a superb job. This potentially saves about £100 on shipping the barrel back and forth to the US.

As I have said before, nearly all of my problems have been self-inflicted disbelief Good learning experience though biggrin

Brian



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Robert Lithgow wrote:


I have a 2006 TTR that I have had from new. Since it is now probably worth only about (NZ) $ 2 - 3 k I am investigating a big bore kit to boost the power. I am not able to take the top end to the USA. Maybe I should bite the bullet and frieght it there.

But I have a son who is a mechanic and I am trying to get clear what exactly is involved. Discussion threads about wrong sleeve lengths and having to champer the barrell makes me concerned about the completeness of any kit received and the exactness of accompanying instructions.

On your comments you talk about "machining the crankcase and fitting new bearings - what is that all about ? Is that a necessary thing or something you had done to rebuild an old engine ?

Any insights to the big bore process gratefully received

On a recent off road/dirt road/ 5 day trail ride I decided a wanted a bit more power. I am also palnning to strip more weight off by removing carrier and numberplate mountings etc and generally get bigger rear cogs and orientate to more dirt and better climbing. I am familiar with the thing and KTM's are unreliable and don't want plumbing from water cooling so going to spend some money upgrading the TTR. Compromises would be the WR250R or the KTM Freerider but the arithmetic/benefit ratio is hard to justify.

----------------------------------------------------------------------------------------------

Hi Robert - I think I have successfully moved the relevant bits from your other message.

Hopefully, Thumper sending me the wrong length sleeve was an aberration and won't be repeated with other customers! 

In retrospect, I might not bother with chamfering the barrel on a future build. Thumper don't do it and, if the sleeve is fitted properly and glued in with Loctite or similar, then there shouldn't be a problem with oil weeps. I guess I was a bit paranoid after my first experience with the cracked barrels. 

The new sleeve is quite a bit wider than the original and won't fit the "mouth" of the crankcases hence they have to be machined out. Although not recommending it, Thumper Racing did tell me that some owners have done this using a Dremel.

If you use a sound engine then you probably don't need to replace any bearings or rebuild the crankshaft. In my opinion, the TTR250 engine is over engineered and that even a well-used (not abused!) engine should take the 325 strain with no problems.

With regard to the WR250R, I have one and it is a complex bit of kit (compared to the TTR) and just about everything takes twice as long e.g. to fit longer throttle cables for my Dakar bars required removing rad shields, rad protector and the rad mounts themselves to allow it to swing back to access the cable run which is through a hole in the frame no

The Freeride seemed a good idea but suffers from a small tank and very short range plus it was really intended for more technical going and hasn't really got  the legs for what most of us do with our TTRs. In the UK, the Freeride is an ideal LDT (Long Distance Trial) steed.

Happy to help with any questions (if I can!) but I hope that other 325 owners will contribute to the discussion.

Brian



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Hello Robert
I converted my bike to a 325 about 9 months ago and as Brian says it does transform the bike if you are looking for more grunt. Luckily I was able to learn from Brian's early troubles and the engine thus far (about 1500 miles) has been fine without any oil leaks etc. It doesn't seem to use much more fuel, starts fine and runs well at very low and higher speeds. The only downside is that it isn't as smooth as the 250 but thats probably my fault. I should have converted a known engine instead I took an unknown, changed nothing and rebuilt it with the 325 kit. Its probable that there is some wear in there somewhere which I didn't pick up on. The joy of the TTR is that you can do all these modifications and its just so easy. To have something new just to throw down a track is alien to me so having this option for more grunt was perfect.
Your son will be able to follow the excellent "janet & john" Yamaha maintenance manual to do the strip but I didn't pull any bearings from the crankcases before machining. I washed and washed them then covered as much as possible with duct tape which stoppped the swarf getting around. After the machining I washed the cases thoroughly again. I would suggest you do the chamfer whilst you are having the crankcases machined. I didn't so couldn't use the o ring between the cylinder barrel and the crankcase. Instead I used a lot of RTV sealant which doesn't look brilliant. After that its a straight forward rebuild. The manual specifically deals with stripping the engine and rebuilding and its very well illustrated and easy to follow.

Wish you luck and hope you do it and its well worth it.

Cheers

Simon



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I have a TTR 325.  Thumper Racing put mine together for me so I've had no issues whatsoever with the engine.  However, I can't get the jetting right.  I have a bog under part throttle.  It runs great under full throttle.  I've change out the main jets 3 times (I believe 137, 142 and 147 and tried several different pilot jet sizes.  I've also changed the clip position.  Any ideas?  Has anyone tried a Mikuni flat slide in place of the stock carb?  



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rhughes43 wrote:

I have a TTR 325.  Thumper Racing put mine together for me so I've had no issues whatsoever with the engine.  However, I can't get the jetting right.  I have a bog under part throttle.  It runs great under full throttle.  I've change out the main jets 3 times (I believe 137, 142 and 147 and tried several different pilot jet sizes.  I've also changed the clip position.  Any ideas?  Has anyone tried a Mikuni flat slide in place of the stock carb?  


 

First of all... Changing your main jet size or clip position will NOT fix the problem described.

Things to try...

Remove carb & connect the fuel line.... Does it squirt a nice stream out from your starter jet /fuel pump?

Posted Image

If so & your carby is clean & there are no other symptoms then it suggests that your pilot jet is too large or blocked.

I would add more to this but maybe you could start another thread? so as not to plagiarize this topic.



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Wanted to revive this old thread. Thinking about the 325 kit. It has now been some time, would like to know if anyone is having any problems with the 325? How has it lasted over time?
I live in the US so I am thinking about just sending the whole engine to Thumper Racing. Kind of figure I would screw something up. I do want to learn but I would prefer to ride.

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It should be lots of petrol burned since the first posts.

How are 325 engines lasting? Still alive? :)



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Welcome to the forum Honda15i biggrin

If Thumper Racing send the correct size sleeve and you have it fitted by a good engineer then you will have no problems biggrin

I can't immediately tell you how many trail miles mine has done but have had absolutely no problems with it other than a puff of smoke on start up occasionally. The engine doesn't use oil so I haven't been concerned about it. An old biker buddy says that is a characteristic of Wiseco pistons....

I love the extra torque and it can pull my porky 18 stone around with remarkable alacrity wink

It would be interesting to know how many other active forum members are running 325s. Mossproof is the only one that I know of for sure.

Brian



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Welcome to the forum Arthur. handshake.gifNice to have you.

Be sure to introduce yourself in the just joined section. We love hearing about intentions and perhaps seeing a photo or two.winkbiggrin

smile



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Still have mine running well although not using it too much. Starts easily, runs well, doesn't smoke, just as before its just not as smooth as the 250. I ride a standard 250 through most of the winter crud on the road so have a regular comparison.

All in all worthwhile however I would recommend starting with a known engine as stated before

Cheers



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Done about 3000 miles on mine. Currently suffering a funny knocking sound which I have a horrible feeling may have been caused by running low on oil over a 3 day laning and motorway thrash. Beginning a tear down when I can gather the nerve, but it appears NOT to be crankshaft related (and may even yet prove to be external - I live in hope!) but is proving very difficult to diagnose. Anyhow, it's not the fault of the 325 conversion, which I love and happily recommend provided it's done properly as covered in Brian's posts on the subject.

Ride safe,
Simon.

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Well, I did a complete tear down. The only wear on the big end pin was where the thrust washers spin, ie none on the bearing or bearing surfaces at all. No wear on the little end (gudgeon pin) Slight ovalling of the barrel but not enough to cause piston slap. One of the crank bearings felt a bit lumpy, but this might have been dirt dropped into it during the tear apart. It had no play in it but I replaced it anyway. Gearbox bearings all ok.
Sooo, whatever my noise was/is, it appears not to be internal. Still happy to recommend the 325 conversion.
Simon.

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lovely

www.youtube.com/watch

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Yep can highly recommend this mod. It has a surprisingly large effect on the power and torque output. It's in storage now but did 2500 miles with no problems other than one minor oil leak from barrel crankcase interface. No smoking on startup or running. Doesnt seem to use any oil. Built this from an unknown engine which may not have been the most sensible thing but it does work well. No problems with original starter. Think it's better on fuel than original due it's plodding nature. I use 98 octane.

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Hi Guys 

I'm also thinking of heading down the track of the 325kit , I'm needing a little more down low 

What Jet sizes are you guys using ?

Cheers Marty



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Hi Marty and welcome to the forum!

See this thread http://ttr250.activeboard.com/t56824181/325-kits-whats-involved-from-a-uk-perspective/ and scroll down to mossproof's post of 12th July 2014 where he gives dyno results and jetting info.

On my own 325, I have tested about half a dozen refurbished carbs on it recently and the 325 ran well with all of them despite them having different jetting combinations. I run the standard airbox with a TwinAir filter and a Motad exhaust.

The 325 doesn't seem too fussy about jetting it seems and, if anything, runs a tad rich on the standard main jet and running can be improved by raising the needle a notch or two to lean it out.

I have a recollection that the jets supplied with the kit weren't genuine Yamaha ones so I didn't fit them.

Brian



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I'll take a look at it
I like the 250 but more low down grunt is what I'm after
Marty


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Would a WR250 front end , tripple camps and forks and rear swing arm fit onto a TTr250 ?

cheers M



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Hi Marty - prolly best to start a new thread or add to an existing one.

Lots of info here http://ttr250.activeboard.com/t63307979/05-yzf250-usd-front-end-meets-ttr/

It includes the dimensions of the TTR headstock etc so you can compare it with the WR2450 but YZ seems the way to go.

Brian



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