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I have just done a bit of research for a customer so thought I might as well share the information and maybe there are owners on here that can add to it or correct it - please!

The only big-bore kit I have found for the TTR250 is from Thumper Racing in the States - see http://thumperracing.net/index.php?route=product/category&path=37_43_107

Thumper charge $440 plus shipping for the kits – shipping to the UK is about $65 but you don’t see the amount until confirming an order and I wasn't prepared to do that to get the latest price! Total approx. $505 which equates to £304 at 1 USD = 0.601721 GBP. The exchange rate is quite good for us in the UK at the moment so, if you are going to go for it, now is the time!

On top of that basic cost would be import duty and VAT at 20% plus a Parcel Force admin charge of about £12 - approx £72.80 plus possible Import Duty but that's not clear. Parts I buy from the States have Import Duty some times and other times not...

Grand total £377 approx.

Pressing out the old sleeve, machining the barrel to take the oversize sleeve, pressing the new sleeve in and then boring it for the new piston would likely be £140 - maybe less. Thumper Racing will do the installation if you send them over your barrel. I recollect they charge about $150 (about £90) plus you have to add the cost of shipping your barrel to them (about £25).

The innards would need to be taken out of the crankcases and the mouth bored to take the oversize sleeve - approx. £55 plus the cost of any new bearings and seals required on the rebuild.

The crankshaft big-end bearings and the conrod's little end need to be in good order to take the additional stress. These can be checked when the crankcases are stripped out.

So you could have a TTR325 for less than £600 if all went well and all your existing parts can be re-used.

Still cheaper than selling the TTR and buying an orange bike....

Brian

PS This is what I got in my 325 kit. It was missing the air filter which Thumper Racing sent on later.

325kit 001.jpg



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Brian - if you were to summarise, what would be the advantages/benefits to carrying out this modification? How do the characteristics of the bike change?

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The simplest summary is "more torque"!

A lot more fun to ride and a more suitable engine capacity for both my weight and the TTRs wink

Brian



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you find the front tire rarely touches the ground.
I have the 325 kit and its got loads more torque. i can only imagine a set of aftermarket cams.
be wary as i am a victim of the common barrel cracking. I does not affect performance. just have to clean her up twice as much
its outfitted with 14-42 gearing and can still get the front tire up in 4th, and 5th gear. and plenty capable of hwy speeds.



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If anyone buys a kit from Thumper Racing then please check the liner dimensions BEFORE fitting the liner.

I reckon the dimensions should be:

86mm o/s diameter

Height is 101.70mm

Shouldn't get any cracking of the cylinder barrel when fitting if the o/s diameter is correct and the engineer uses his noddle when boring it wink

Did you make a note of the o/s diameter of your liner by any chance Mingle?

Brian



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A mod i will consider in the future ,i has thought about getting a wr when i got better at riding and funds would allow but this seems a better option as for similar if not less money i could keep my bike and have a new engine and not buy something else with the problems ive already spent money fixing on my ttr

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I have thought about this mod but am very worried about the ''barrel weep'' problem. Some say it can be rectified but I have not seen or heard of one that does not have this problem (oh wait, maybe one). If I did not have to compromise the reliability of my engine, I would consider this more seriously.

Jarrah 



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I know of two 325s with no leaks within a 10 mile radius - mine and Chancey's biggrinbiggrin

Plus at least one other belonging to rhughes43 wink

The problems were down to a batch of oversize liners that Thumper sent out to customers a couple of years ago no

Brian



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So i assume they have that sorted now and the problem was down to the barrel being machined as per the instructions and the machineist not measuring the OD of the liner ?

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That's about it. The liners/sleeves supplied had a bigger o/s diameter than could fit in the TTR barrel. Once the barrel was bored to take them, it left the aluminium wafer thin between the fins which soon cracked and allowed oil seepage. That's why I have given the correct dimensions for the 325 liner so that anyone buying a kit can check before fitting their new liner wink

We used a non-motorcycle engineer to do the work and they didn't check as they assumed we knew what we were asking for. In our defence, we hadn't seen a 325 kit before and had no idea of the problems ahead no

On the positive side, I have had liners supplied since and they have been OK. We have also used machine shops that do a lot of m/c work.

Brian



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Sounds good i think this is going on my list of future mods as i do like my ttr ,im taking it out tommorow to show up some ktms biggrinbiggrin



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It would be nice if the kit came with a thicker cylinder Barrel so that the leak problem was completely solved!



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Ah - I see what you mean Paul. No pics of a bored out barrel before the new liner is pressed in as the operation is done in one session by the engineering firm.

I did investigate having some thicker barrels cast especially for the 325 conversion but the set up costs were quite high plus the machining needed after casting. I wasn't confident enough about the demand to go ahead and have a batch made up.

I am not a trained mechanic and have no insurance etc in place to offer a fitting service - sorry! 

In any case I have over a year's work of my own waiting to be done wink

Brian



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do all the barrels crack in the same place when they do crack ?....
the pics I have seen.. It looks possable to run a weld in that area
before the old sleeve is removed....

No it won't warp if done right.... 

heat the barrel to 500 deg or so in a oven prier to welding...

then the diffents between the barrel & heat efected weld zone is less...

then back into the oven to cool slowly...



-- Edited by petenz on Tuesday 27th of May 2014 06:50:18 AM

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That's a good idea Peter. I am not an engineer so wouldn't have known that.

The area is deep between the fins. Would there be enough room to weld?

The pic below shows the area of the barrel that can crack. Hopefully you can see the hairline cracks on the 2nd, 3rd and 5th fins down.

It's only on the LH side of the barrel that the weeps occur. Everywhere else seems fine. Remember that the pic is from a barrel where Thumper had inadvertently supplied a sleeve that was too large an OD.

Leaking barrel.jpg

 



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TTRfan wrote:

 

The area is deep between the fins. Would there be enough room to weld?

 

Leaking barrel.jpg

 


 The deep fins could work for yer...

with a Tig welder you would need a lot of needle stick out... that usaly makes it hard to

retain the gas sheild.... but the fins would hold the gas there....

The same with a mig welder... a lot of wire stick out.. but the fins would retain the gas sheild..

You would need to get in there with a die grinder or dremmal and give the area a good clean up

before welding to remove any risk of contamination... ONLY use carbite burs.. grinding stones etc

leave carbarundum etc inbeded in the alloy..



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TTRfan wrote:

 

I did investigate having some thicker barrels cast especially for the 325 conversion but the set up costs were quite high plus the machining needed after casting. I wasn't confident enough about the demand to go ahead and have a batch made up.


Brian


 I think if you did go ahead with making the barrels, people would become interested. The only thing that stops me is this cracking issue which there is still no guarantee that it will not happen.

If the barrels are not worth a pot of gold, I'll take one no problems. smile

Jarrah

 

 



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Serious question Jarrah. What would you be prepared to pay for a newly cast thick-walled barrel with all the machining done?

Brian



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If it was a complete kit I would pay from $600- $700 AUD (£330.064~£385.580 GBP).

For just the barrel I think it would be worth $300~$400 AUD (£165.255~ £220.340 GBP).

Not sure if that makes it viable or not though?

If you did end up having the barrels made up, maybe you could make them to fit up to 350cm3? It would be worth paying extra if this is possible.

Jarrah

PS. If you want to type a pound sign with an Australian keyboard (we do not have the pound sign), hold down ''Alt'' and type 0163 with the numeric pad. Note: you cannot use the number row at the top of the keyboard. Some laptops require you to hold down ''Alt'' and ''Fn''.

 



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For those interested in the 325, I shall now attempt to attach printouts of a couple of dyno runs I did on my 325. Unfortunately, I neglected to do a pre modification run to compare disbelief but the results may be of interest...

First set: Standard exhaust and airbox with Twinair filter. Pilot jet 50, main jet 147, needle clip in the middle slot. (For the record, this is a '93 Open Enduro and was a pretty much standard bike)

 

  Sim 001.jpg

I then went home, raised the needle clip one notch in an attempt to reduce mid range richness. Fitted a lovely Brian/Motad tailpipe and replaced the snorkel in the airbox with an oval tube the same overall length and outside diameter (increases internal swept area a bit without widening the hole, also no significant noise increase) The following is the result...

YamTTR_250.jpg

Another horse and a bit, slightly lower torque, still running fairly rich (13 being optimum). Most noticeable is all the curves are smoother. On the road difference is not great, except in my head!

I may try increasing the airbox aperture a bit more as I hate wasting fuelbiggrin but not 'till after the VINCE next week!

Also of note: I had the barrel weep issue as this sleeve is the "wrong" diameter . Removed the sleeve and pressed it back in with Loctite Green stuff, and put a bead of Loctite 5910 flange sealant where the base o-ring used to be, also thin smears of 5910 on the 2 head bolt washers under the cams and on the head gasket around the cam chain gallery. Despite the fact that you can actually see the sleeve through the wall of my barrel, I am nearing 1000 miles with no leak. I think with the correct o/d sleeve bonded in with Loctite green the problem might just be kept at bay. 

Fantastic engine. I'm sure with Jarrah's attention to tuning and a louder end can you might even get to the magic 30 at the rear wheel?

Ride safe,

Simon.

 



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Honestly, I considered this mod. But IMO, between the headache, the time, and money that's involved with this, I would MUCH rather put my time and money towards a more capable dirt bike. Like a KDX200/220 or WRF. I don't think that there's any mods out there for the TTR that can make it comparable to a Good KDX or wrf. Well, maybe the wr400f. They work good, but they're no WR426f. It's surprising how much more better bike all around a wr250f is compared to a ttr250. No money and/or time could ever make the ttr comparable.

Really? A barrel weep issue cause the sleeve was the wrong diameter? Sounds like a nightmare! All that time and money only to recieve a headache. I hope you guys don't take any offence to this, but honestly, save yourself the trouble if you're considering this costly/timely/frustrating mod.

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+1 on the above



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Terrence R wrote:

Honestly, I considered this mod. But IMO, between the headache, the time, and money that's involved with this, I would MUCH rather put my time and money towards a more capable dirt bike. Like a KDX200/220 or WRF. I don't think that there's any mods out there for the TTR that can make it comparable to a Good KDX or wrf. Well, maybe the wr400f. They work good, but they're no WR426f. It's surprising how much more better bike all around a wr250f is compared to a ttr250. No money and/or time could ever make the ttr comparable.

Really? A barrel weep issue cause the sleeve was the wrong diameter? Sounds like a nightmare! All that time and money only to recieve a headache. I hope you guys don't take any offence to this, but honestly, save yourself the trouble if you're considering this costly/timely/frustrating mod.


 From that statement you OBVIOUSLY have not ridden a WR400 (at least not mine). Considering that they were not made for Canada, I actually doubt that you have ridden either bike.

They are just as capable as a WR426 and pull just as hard. Mine gets a top speed of 170kmh with 14/50 sprockets, which my mate with his modified WR426 can only dream of (or my mate with the fastest WR450f which is the 06 model).

All depends on how you set up a bike in the end.

I do agree with the rest though.

Jarrah

 



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Hi Terence

Your comments make complete sense IF you are looking for a pure off road steed.

I had a KDX200 and it was great on the dirt but a total pig on the tarmac. I also know this from other owners who experienced the same. They hunt on constant throttle and are only really happy with the throttle wound on. Same with an RM250 and a KTM 200EXC I rode for a while - neither made good trail bikes as they really really didn't like doing road miles cry

The WRF is also a fantastic dirtbike (I also ran one for a year or two alongside my TTR) and was great for events but not so good for trail riding. If geared for the lanes it was a buzz box on the road (only 5 gears) and would burn your arse off after 5 or 6 miles of tarmac no

The TTR is a proper trail bike with 6 gears and good road manners. The 325 engine just makes it soooo much nicer biggrinbiggrin

Just my two penn'orth wink

Brian



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No offence taken. If you enjoy playing with engines, the barrel weep is frustrating yes, but not a nightmare, just a challenge to be solved. If I wanted another bike, I'd buy another bike. I love my TTR - how it handles, how comfortable it is and how it looks. Giving it a bit more grunt is just my way of lavishing attention on it! BTW, the barrel weep issue is only because we're trying to "push the envelope" with what is possible with the standard engine. I could probably squeeze a DR650 lump in there, but that's a different challenge altogether...

It would be a dull world if we all did/liked the same things!

Simon.

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Or just bore it to the max 2mm oversize like I did, really happy with the bikes performance and no issuessmilesmile Simples.

But then I had the luck or borrowing  Bri's bike for the day, did not give it the full beans thoughcrycry to appreciate that extra power, maybe next timewinkwink

Nice bikesmilesmile



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This still in trial mode or ready for the masses?

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The kit's been available for a while. The tricky bit now is getting Thumper to send the correct parts! It is a lot of faffing about to get the engine cases bored out but if you like projects...
TTR Steve's option is the next best thing - basically just a top end rebuild.
Thinking of doing it to that Scottish bargain ?
Ride safe,
Simon.

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mossproof wrote:

The kit's been available for a while. The tricky bit now is getting Thumper to send the correct parts! It is a lot of faffing about to get the engine cases bored out but if you like projects...
TTR Steve's option is the next best thing - basically just a top end rebuild.
Thinking of doing it to that Scottish bargain ?
Ride safe,
Simon.


 Crossed me mind to do it with the blue un, a bit more oomph and a mini supermoto jobby  



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whats the biggest the standard liner can be bored to safely...

dose anyone know the OD of the standard liner?



-- Edited by petenz on Thursday 21st of May 2015 06:59:06 AM

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I think the biggest you can go on the standard liner is +2mm which gives you 263cc - see here

The piston set was sold as a"280 kit" but my calcs only show 263cc. Happy to be proved wrong though!

Those that have chosen this option have been happy with the results the extra 5 percent capacity gives.

OD of the standard liner is 78mm.

Brian



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TTRfan wrote:

I think the biggest you can go on the standard liner is +2mm which gives you 263cc - see here

The piston set was sold as a"280 kit" but my calcs only show 263cc. Happy to be proved wrong though!

Those that have chosen this option have been happy with the results the extra 5 percent capacity gives.

OD of the standard liner is 78mm.

Brian


 I get the same as you with the 74.95 piston.... 263cc

useing..

3.1415927 x Radius x Radius x length

3.1415927 x 37.5mm x 37.5mm x 59.6mm = 263cc

 

To get 280cc you need a 77.5mm bore...



-- Edited by petenz on Thursday 21st of May 2015 08:43:58 AM

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How does this effect 0-60 biggrin



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5% quicker biggrinbiggrin



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