A forum for owners of Yamaha TTR250 trail and enduro bikes!

Gadget964 · Veteran Member

350cc Big Bore Kit for the TTR250 - updates and gossip!

Kaos · Senior Member

Sounds great, is it still got the original carby or the Mikuni? How did it run?
Where were you riding, up Mildura way looks like Mallee scrub.?

Gadget964 · Veteran Member

Still original carby at the moment, waiting for the Mikuni to arrive. It just feels like it has more to give... But apart from some wide open deceleration issues, I'd say the carb is currently set pretty well.

And yes, Sunset Desert. Just a little play as a shakedown before doing anything too big.

Liam & I both broke mirrors on trees today as we were riding on some pretty tight, whooped out tracks; so shopping tomorrow for replacements. Also on tomorrows agenda, is checking to see if anything came loose. Nothing obvious so far, but will check.

ttr steve · Super Guru

Good news, I am sure you will get bike fit soon smile

mossproof · Super Guru

I like the torque so much I didn't want to risk losing it by opening up the top end, which is somewhere I rarely go.
Glad to see you're running her in gently

Gadget964 · Veteran Member

Another 286km yesterday. Running sweet, averaging about 15km/lt. I lost a header shield bolt.

The difference between the two TTRs is amazing. My son is now looking to trade his TTR 250 for an XR 400 or similar.

Apparently my new carb is at home waiting for my return.

-- Edited by Gadget964 on Saturday 6th of June 2020 01:02:57 AM

-- Edited by Gadget964 on Saturday 6th of June 2020 01:16:55 AM

Kaos · Senior Member

Great result glad its running well. I'm riding up there in August doing a Mildura - Murrayville return, two days. biggrin But Hattah is cancelled
It will be interesting to hear how the new carb effects performance. Are you going to open up the airbox more, bearing in mind there's been a 40 percent increase in displacement?

Gadget964 · Veteran Member

The airbox lid that's on it has two holes in it... With the way that the bike already runs, I doubt that it will need any more. I will also try it on an unmolested lid as well.

Gadget964 · Veteran Member

Mikuni is in.

Only been run in the shed so far, but very snappy response.

Kaos · Senior Member

Was it an easy bolt in?

Gadget964 · Veteran Member

Throttle pull is on right side, so needs a bit different angle to get it in. Not difficult, just different.

To allow for the right side pull, you also need to modify right-upper engine mount (I just replaced it with a spare left sided mount that I had) and an little position adjustment of the shock reservoir mount.

ttr steve · Super Guru

How much was the Mikuni please and why change over to that carb?

Just interested.

Gadget964 · Veteran Member

I just had a whole heap of stuff typed, then my old man rang.. So I lost it all and have to start again.

I'd always planned on going to a bigger /better carb when I was setting up the 350. Theoretically the Mikuni will really "wake up" the TTR... With the 1/4 pull throttle and pumper it should give the bike a bit more snap off the bottom. My son mentioned that it feels like it has more to give after riding it last week.

www.mikunioz.com/shop/yamaha-ttr-250-mikuni-tm33-8012-pumper-carb-kit/

TTRfan · Super Guru

Gutting when you lose something you have put thought and effort into Mark cry

There will be a lot of interest in your carb conversion and, cheeky ask I know, would you be willing to start a new thread in the Carb sub forum please?

You have put some great photos on the TTR250 FB Group and, if it helps, I would be willing to copy them over if you start the thread?

Cheers

Brian

Gadget964 · Veteran Member

You can add to the carb threads if you like Brian. As general fitment, it can be used for all TTR250/350's. But from my perspective, anything that happens to the carb from the initial fitment, will be specific to my 350- so may not be relevant to 250's (or those at different altitude or humidity). It will be interesting to see how it goes on the road in the next few days. Once tuned, I'll be getting another dyno done.

Even with the standard carb on, the 350 kit has a significant- seat of the pants- gain over the 250. Every now and then I get asked if it's worth it... Hell yeah. Granted that there is a significant financial hit (especially with poor exchange rates and import duties- I could buy a low Km DRZ400 for what the motor cost to get done) But this bike is something really special, and in its current configuration its helping to draw attention to the Totally TTRs 350 big bore kit.

tripodtiger · Senior Member

Your son looks like he's more in control of the beast (see photo in AdvRider).
Bloody kids!

Interesting that the stock carb was only giving 15km/l. Wonder if that had much to do with your right wrist on your new old bike?

Gadget964 · Veteran Member

150 km per tank is all we could get on any of our TTRs. Sand takes a bit of work.... And yeah, playing with the right hand.

Gadget964 · Veteran Member

I managed to get the bike out for a short run yesterday. The Mikuni definitely gives more punch off the bottom. I never went to WOT, but mid-upper needs dialling in. I have the AFR meter in the shed now, so once I get a heap of spare parts tidied up, I'll be able to get connected.

For the brains trust: What do you recommend my target range be? And just confirm for me that low number =rich, high numbers =lean.

mossproof · Super Guru

Correct - low=rich, high=lean.
Anywhere below 11 is wasted fuel IMO. I felt that above 13 in the mid range felt flat although it is still on the rich side of stoic - the supposed "ideal". I feel most comfortable in the mid 12 range, which is a compromise between best rich torque and best power at WOT according to the SAFR website I linked a few pages back, with enough richness to help keep combustion temperatures reasonable.
Of course, the pumper confuses the issue by lobbing in more fuel unmetered when you twist the throttle, so you want to be measuring at steady rates I think. If you get 12 - 12.5 while clinging on with the throttle full open, and 12 - 13 at tickover, then start playing with needle position for the best "feel" in the mid ranges, and fuel screw for the best "zap".
Welcome to the merrygoround - change one thing, affect something else unexpected, start again...! Keep a note every time you change something - it all becomes a blur after a while!
Good luck, it'll be worth it.
Stay sane!
Simon.

Gadget964 · Veteran Member

OK. First issue was not wiring correctly... Got that all sorted and the AFR calibrated, then with the bike running at idle had an afr of 22.4... Hmmm, that's the same base reading it has when exposed to air (I'm using exhaust tip meter - at the moment) I re-read the instructions= air leak in system. Apparently they were right, I found a really crap connection between the header and muffler. Pulled that apart and re-realed. I will start again tomorrow.

mossproof · Super Guru

Just found your Advrider thread Gadget. For those without the patience to search:

advrider.com/f/threads/project-ttr-350-because-i-can-because-i-want-to.1441829/

Think your lad will be dissappointed by an xr4, but he looks like he's got the skills to make it work!

Does your afr pickup sit at the end of the tailpipe or have a sniffer tube you insert? I'd be interested in the details.

Forgorin · Senior Member

Well, number 6 is on the road. I've put 100 km on it is far. I have not 'opened' it up yet but, it sure does have much more grunt low down. Ive got a standard airbox and a free flow exhaust. i haven't done anything to the carb yet. Perhaps this weekend after I have a few 100km done. It does stumble a tiny bit if I blip the throttle. I assume I can fix that with the air screw.

Anyways, was a tough trial getting it built with some trouble shooting thrown in. I doubt I could have done it with out the existing threads here on the forum and help from various inmates. Thanks sooooo much guys. I can't wait to be able to put the bike through it's paces.

P.S. My raid has a new name Nessie. HEHE

Gadget964 · Veteran Member

Little sh** has skills alright... It's a disappointing, but bloody good feeling when your children can out-ride you.

I've just been looking at the AFR again, I'm getting inaccurate readings from the sniffer tube at idle... So I've just mounted the plug on an old header. The recommendation on fitting for mine was 24" from exhaust port, which puts it at the start of the heat shield.

-- Edited by Gadget964 on Tuesday 16th of June 2020 02:06:29 AM

-- Edited by Gadget964 on Tuesday 16th of June 2020 02:07:03 AM

Forgorin · Senior Member

I'm looking forward to how it works out. It's a shame you couldnt get a before and after dyno run.

Gadget964 · Veteran Member

Not a bad thought. I had a dyno done in 250 form... I might see how receptive they are for letting me change carbs and doing a Teikei v's Mikuni run (it shouldn't take me too long to swap over.

mossproof · Super Guru

Well, it's been a week. Did you blow it up at Hamilton Gadget?

-- Edited by mossproof on Thursday 25th of June 2020 09:16:07 PM

Gadget964 · Veteran Member

Didn't end up taking it- Sold my sons TTR, dropped that off in south west Victoria (they paid for delivery!)- then ended up in the middle of NSW to pick up his next bike (about 2000km loop all up). After riding my350, he wanted a few more cc, so ended up with an electric start XR400.

I'm pretty sure the 350 will get out in the next few days. The bike has 11.5 hours on the meter now. I'll get a few trail rides in to make sure that I'm happy with the way it's running, then re-check AFR...... Then Dyno again.

I did manage to get my new tank fitted though:

-- Edited by Gadget964 on Thursday 25th of June 2020 10:33:00 PM

Kaos · Senior Member

I'm still loving your bike. Be interesting to read the dyno result and comparison with the XR400.

oki · Newbie

Hello
My TTR uses the Kawasaki ZX11 piston
Displacement is 270cc
Carburetor uses Mikuni TMR32
Very satisfied, but also very interested in the 350cc kit
But it looks like it's sold out
It's a very attractive kit
Do you plan to sell it again?

ttr steve · Super Guru

Welcome to the forum M from Japan smile

We hope to be doing another run of 6, just checking with the foundry, they have sold very well and 13 x 350 kits are now out in the world smile

oki · Newbie

Thank you for providing a great product
I am very happy to be resold
I definitely want to buy it

My TTR has the starter motor removed
We plan to combine the 350cc kit and FCR-MX(37mm)
I'm looking forward to seeing what kind of TTR it will be

Thank you

Gadget964 · Veteran Member

Only a little run today, needle lowered one clip position. The mechanic that built the motor was reluctant to get off it. He said "I could ride this bloody thing all day"

So my son told me today that I'm racing the TTR next month at the Farmers 6 hour enduro... After tomorrows ride I guess I'll be pulling out the suspension to get it dialled to suit the bike.

ttr steve · Super Guru

Awesome, let us know how you get on smile

Millwoodva · Newbie

ttr steve wrote:
Welcome to the forum M from Japan
We hope to be doing another run of 6, just checking with the foundry, they have sold very well and 13 x 350 kits are now out in the world

Any update on the 350 kit availability? Deposit required?

mossproof · Super Guru

New batch of castings being heat treated today. Run of 6 - small enough not to frighten my machinist (doesn't take much!) large enough to reach min order quantity for custom pistons. Going on past experience, expect a couple of months to pass before they're ready!
Steve at www.totallyttrs.com deals with sales: sales@totallyttrs.com

IanU · Member

oki wrote:
Hello
My TTR uses the Kawasaki ZX11 piston
Displacement is 270cc
Carburetor uses Mikuni TMR32
Very satisfied, but also very interested in the 350cc kit
But it looks like it's sold out
It's a very attractive kit
Do you plan to sell it again?

Hi Oki,

Is this just a 3mm overbore, or are other mods required to fit the ZX11 piston?

How does this affect the compression ratio?

dlee22 · Senior Member

One of my ttrs had a zx9r piston, trouble was it was warn and burning oil so never found out much about it myself but apparently the previous owner was competitive in the enduro class he raced in.
. Glad someone else found a similar modification.

oki · Newbie

IanU wrote:
Hi Oki,
Is this just a 3mm overbore, or are other mods required to fit the ZX11 piston?
How does this affect the compression ratio?

Hello IanU.
Cutting the top of the piston.
There are also Japanese shops that sell cut pistons.
http://hpo-japan.com/service/ttrboaupkit/ttrboaupkit.html

The calculated compression is about 11.8:1.
RC-SUGO (YAMAHA racing parts) high lift camshaft is also used.
I think the actual compression is not so high due to the influence of the high lift camshaft.

IanU · Member

Hi Oki,

Many thanks for the reply, interesting information.

Ian

Christos · Veteran Member

Any Dyno graph available at this point with the Micuni carb? Final jetting and air screw position? @Gadget?

Gadget964 · Veteran Member

Not yet- after the last ride (July 4th) I pulled the forks out so that they could be re-chromed and serviced prior to racing in a 6 hour Pony Express on August 15...... The race was cancelled due to Covid-19; but for some unexplained reason, my suspension tuner is yet to get the forks back from being re-chromed, despite making regular calls (I think that it's the last business that my tuner will ever send them). So the bike is sitting in the shed with two new tyres, home made steg-pegz, a salvaged Staintune muffler (that had been left without a bike due to the bushfires last summer), and no forks. Very annoying.

Christos · Veteran Member

I hope you will get the forks back soon, such delays are annoying, the bike sitting there instead of riding it!

mossproof · Super Guru

I feel your pain Gadget!
Chrome finishers are from the same school as foundry workers in my experience. It'll happen when it happens, you just have to wait

New batch of 350 barrels ready for machining. Realistically likely to be ready mid/end of October.

Now that someone has appeared on the forum with an efi converted ttr engine, anyone want to have a go at it on a 350?

Gadget964 · Veteran Member

We are still under covid restrictions here at the moment, so I probably wouldn't be able to do too much with the bike if it was complete.... But it will be good to get it back together. I am so keen to try out the changes, and to get the dyno done.

It probably wouldn't be so bad if I hadn't been waiting for parts for the Tenere, WR200, and XR 400 for the last month/6 weeks as well.

It's good that there is enough demand on the 350 to continue with production in small batches. I'll stick with the Mikuni thanks - no way I'm screwing with EFI.

-- Edited by Gadget964 on Tuesday 1st of September 2020 09:41:22 PM

robs · Senior Member

Hey all, great to see you're still making new ones of these mossproof! I think I asked a while ago but I was wondering: I have spare engine casings (originally intended for a 350 conversion) - would anyone be willing to convert my TTR to 350 over winter? Obviously I'd pay well for labour.

I love my TTR and have been really interested in this thread for years but just don't have the time to do this as a project myself. If anyone is interested please DM me!

TerryK · Super Guru

Guys I have come across TT350 decals

Elite design Co.

elitedesignco.com.au/1986-yamaha-tt350-replica-oem-tank-graphics/

Cheers Terry

Gadget964 · Veteran Member

Hi Terry,

You can get complete kits for the TT350. I used this one(scroll back through the posts): https://www.ebay.com.au/itm/stickers-Yamaha-TT-350-1998-stickers-adhesives-stickers-decal/123175996530?hash=item1caddc8c72:g:iNwAAOxyZw5RZq1M

but I did contemplate this one- but opted for the other one due to the race plates: https://www.ebay.com.au/itm/YAMAHA-1986-TT350-DECAL-GRAPHIC-SET-LIKE-NOS/360250736622?hash=item53e09dffee:g:FcsAAMXQoiJRhB8N

On a side note: I finally have my forks back from the Covid paced re-chroming. I will be taking it out for a run in the Sunset Desert again later in the week to check if I need to change tuning now that I have a Staintune muffler and Webbys header. I'm interested in trying different final drive ratio as well. It is currently 14:44, but I have a near new 48t sitting around..........

I touched base with the dyno people today- so hopefully next week I will have the answer that you are seeking. The dyno will be run with the same gearing and tyre as the original run.

-- Edited by Gadget964 on Monday 12th of October 2020 12:22:41 PM

mossproof · Super Guru

Looking forward to seeing the results. Try and get them to superimpose the new power and torque curves over the old ones to get the best idea of what's changed.

Gadget964 · Veteran Member

They were saving the initial dyno in the computer for that reason.

Gadget964 · Veteran Member

Got the 350 out today for its first run in 3 months. I figured out a few things: I am really unfit (old injuries don't help), the speedo is far from accurate - it's reading 20-30kph slow, so on my last run out here when I thought I was cruising on 120, I was a tad over. The 14:48 gearing feels better than the 14:44. It took me a while to get used to the feel of the revalved suspension, new tyres and steg pegz (a lot of changes all at once)

By changing the exhaust system, I think that my fuel mixtures are a bit out... I might just get it checked on the dyno.