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

Gadget964 · Veteran Member

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

mossproof · Super Guru

Looking at that shiny head reminded me I was thinking about head-work back in the mists of time, and the edge that marks the limit of the original bore could be eased to help gas flow from the outer edges of the combustion chamber since the 350 is significantly larger. However, this would reduce the compression ratio. Good for torque, bad for power I believe, so might have negligible gains unless a higher comp. piston is specified.

Discuss:

Looking forward to hearing your results Gadget. Good luck,
Simon.

Kaos · Senior Member

Gadget964 wrote:
The first Australian 350 is nearing completion... And the bike that it is going into is almost ready as well after having a significant facelift.

Well done Gadget I saw the sneak pics will look (and go) good biggrin

ttr steve · Super Guru

Good news Mark, looking forward to seeing it finished smile

Another kit has just landed in Malta, hope Julian the owner will be posting up on here smile

So that's 4 or 5 up and running in the UK, 1 in Japan and 1 in Australia nearly finished and the new one in Malta, oh nearly forgot Brians.......C'mon Bri get on with it!!!

8 x TTR350's now exist in the world

-- Edited by ttr steve on Friday 1st of May 2020 04:54:28 PM

mossproof · Super Guru

I only count 'em when they're running Steve

Mine #1, your's #2, Dan #3, Tiddler #4. Looks like Mark and Michael in a race for #5 unless Simon knows better...

ttr steve · Super Guru

How is Dans? Dan where are you??

dlee22 · Senior Member

Ahhh mines okay, I had it mot'd the day of the uk lockdown.

I did have problems with the cam positions and turned out the tensioner had snapped, replaced it and the cams are still slightly out sadly despite a fairly new cam chain.

I have been tidying the wiring etc for accessories etc as there was a drain somewhere as they were previously on the battery.

I Rigged up a oil cooler on it with a shorty pipe and just concerned that the pipes are close but I'll sort something as my friend Malcolm who used to be on here set his up well with that arrangement.

Next plan is to refit the raid stuff before grabbing an acerbis tank for the next big adventure.

As for the engine I love it, nice an torquey and the higher gears are much more useable. I wonder how it will cope at very high altitudes?...I can't wait to get out and try fine tuning it as I haven't had a chance since i got the Motad. Sadly I have been preoccupied with fiddling with the little c90 we use for stupid races

On a side note my girlfriend has brought a ttr raid (in bits) from a Malcolm, which will be her first project :)

Padowan · Senior Member

Mine is still in the box. Wanna make a start on it, but I need an engineering Co to do my cass bore, so until I know I can get than done I'm in no hurry to dismantle the bike. I also know that when I do that it'll be the start of a likely not and bolt rebuild !

ttr steve · Super Guru

Padowan wrote:
Mine is still in the box. Wanna make a start on it, but I need an engineering Co to do my cass bore, so until I know I can get than done I'm in no hurry to dismantle the bike. I also know that when I do that it'll be the start of a likely not and bolt rebuild !

OMG forgot about you Simon, that makes 9 smile smile

ttr steve · Super Guru

Loving mine, the more miles the more smiles smile smile

Gadget964 · Veteran Member

The mechanic doing the work in mine is apparently just waiting on the casing gaskets to arrive to complete the motor (he's had several parts delays due to Covid restrictions)

The interesting thing about this build, is that he told me yesterday that he can't wait to ride it. I've known him for almost 13 years and I've never heard him say that about anything..... Coming form an ex-factory Kawasaki rider and multiple Hattah Desert Race winner (up until Toby Price came along), that is something special.

These 350s are sparking a huge amount of interest.

ttr steve · Super Guru

Good to hear, I have 2 left on the shelf at the moment

https://totallyttrs.com/epages/699105d9-e4cc-4b32-b236-84e72cd67f84.sf/en_GB/?ObjectID=23761373

Gadget964 · Veteran Member

Just received a call... My motor is ready. But still 450km away. Covid restrictions starting to ease tomorrow, so I may be able to get it this weekend.

TerryK · Super Guru

Will be interesting to read the real road tests, my TTR feels like it has more torque than my WRR but the WRR has more HP...well that a seat of the pants feel. I'm guessing the 350cc TTR will have even more torque & will produce more HP down low than standard but being an over square bore / stroke it may not want to rev.

A drag race with a good standard TTR, 350 TTR & a good WRR would be nice as the seat of the pants feel can be way off. My standard TTR is still better than the WRR on hills, WRR needs to rev & gets wheelspin.

Now if someone could come up with EFI for the TTR to improve the fuel range & power !!!!!

Terry

mossproof · Super Guru

The 350 still likes to rev, but you'll find you don't need to
Dynos are a few pages back in this thread, but Marks will be even better with free flowing pipes and a bigger carb. Low to mid range is MUCH more tractable, where the WR by all accounts you have to keep revving, as you say Terry. Top end is restricted by the airflow so I'm looking forward to #5's results too.

What is the idea behind your 600 headstock conversion Mark? Did I miss a post somewhere?

-- Edited by mossproof on Wednesday 13th of May 2020 09:42:28 AM

Gadget964 · Veteran Member

How can I post big pictures? Mine just come up as thumbnails...Edit: figured it out.

So: My 350 is currently in my sons possession- and will be coming home to me on Saturday afternoon (very early Saturday morning in your time) I want to tidy a few things up on the casings before I fit it, so hopefully Sunday afternoon I will be right to crank it over.

TTR600 front end: Not sure if I mentioned previously, but my son now owns my old TTR250, but has a DRZ400 front end on it... When I used to do desert rides on it, placement of the front wheel when riding was always carefully (and quickly) planned, with the way he has it set up now, it just doesn't matter- hit whoops as hard and awkwardly as you like... just keep the throttle on..... That's what I want to achieve with the 600 front end. They are a bit beefier, so my suspension tuner will be able to dial them in better than he could the standard TTR forks (even though mine had gold valves). One of the things that I was especially after was having more adjustability (compression and rebound) than the 250 could offer... One of the down sides of working with (and riding) my sons race bikes, is that we have figured out that an extra click +/- can make a difference when riding on different terrains. Many years ago ignorance was bliss- It always felt "Pretty good" because I didn't know any better.

Lectron carbs are not being very useful at the moment. My plan for now is to use the original carb to fire the bike up, but I have an RMZ250 FCR that I'm looking to fit if I can. It may be physically too big, but I won't know until I get my motor back.

-- Edited by Gadget964 on Thursday 14th of May 2020 08:14:39 AM

-- Edited by Gadget964 on Thursday 14th of May 2020 08:19:02 AM

-- Edited by Gadget964 on Thursday 14th of May 2020 08:27:30 AM

Gadget964 · Veteran Member

So I promised you all something different with this build:

Here we go:

My 1996 TTR250 when I bought it.

Photo taken today; awaiting the 350 motor.

BRING ON THE WEEKEND

mossproof · Super Guru

That'll confuse everyone. TT350 with estart. They'll ask why I went to all the bother if the factory already did it!

I've just fitted a Mikuni pumper onto an xt225 Serow for a customer. That's another option, if it would fit - quite a bulky carb.

Is there a weight penalty with the 600 forks? Looks lovely by the way smile

-- Edited by mossproof on Thursday 14th of May 2020 09:32:34 AM

Gadget964 · Veteran Member

Didn't check the weights.

Kaos · Senior Member

Looks great Gadget, good looking machine. TT350 with e start and rear disc brake!! And a single carb I'm still fighting my dual carb setup on my TT trying to get it to work.

BTW the FCR won't fit the TTR I've tried with an FCR32 , they are just plain too big, there is hardly any room, starter is in the way and would have to go.
MikuniOz.com do a MikuniTM33 pumper in a kit for the TTR250 (so u know it fits) and includes throttle cables and quick pull throttle.

Gadget964 · Veteran Member

I had my doubts about the fcr fitting, but without having the motor, it's hard to measure anything (the original carb is with the motor, so I couldn't even compare them).

Christos · Veteran Member

Hello all,
I keep track of this topic and the great effort and work for the 350 kit. I would like to see a Dyno graph at some point with a bigger carb and free exhaust pipe. I believe the gains will be significant.
As I saw the discussion on another carb to fit, I would like to say that I have already installed a Dellorto PHF 34mm with pump and have the jetting adjusted. It fits perfectly, the only thing needed was an aluminum adaptor I had made for the airbox collar. The gains especially from mid to top are clearly noticeable.
Steve, Brian and all, keep up and stay safe!

TTRfan · Super Guru

Hi Christos and good to see your first post to the forum.

Thanks for the contribution and your good wishes!

Lockdown has eased slightly in England and I have been out on the road bikes and the TTR325 will be next for an outing biggrin

Brian

ttr steve · Super Guru

Hi Christos

Thanks for the post, remember we all like a photo smile

mossproof · Super Guru

Don't mean to sound grumpy fellas, but can we keep the thread for 350 - specific stuff. It's already a long trawl without general bike pics. Smart bikes and lovely sunsets though they are, "Show us your bike" might be a better spot?
Christos - a pic of your carb modification would be perfectly relevant here

Christos · Veteran Member

My apologies, here it is:

Gadget964 · Veteran Member

Turns out that the Mikuni TM33-8012 Pumper carb that fits the TTR is 'in stock' in Australia, and $471 delivered.... so I ordered one.

I had heard that the Mikuni carbs were a bugger to tune, so was trying to avoid them. But at that price, including throttle and cables, for a carb that will fit without having to make adaptors, I'll give it a go.

Gadget964 · Veteran Member

My motor made it home about an hour ago. I'd forgotten how rough the paintwork was on the head and cases- I'll do a bit of a tidy up tomorrow, and should get it fitted. Not sure about started, but fitted at least.

Even if I do get it running, I can't ride it until a front wheel spacer arrives..... There's always something.

-- Edited by Gadget964 on Saturday 16th of May 2020 01:41:48 PM

ttr steve · Super Guru

mossproof wrote:
Don't mean to sound grumpy fellas, but can we keep the thread for 350 - specific stuff. It's already a long trawl without general bike pics. Smart bikes and lovely sunsets though they are, "Show us your bike" might be a better spot?
Christos - a pic of your carb modification would be perfectly relevant here

Sure Bri can tidy up, as you are right, it is going a bit of piste!

engineer1949 · Veteran Member

just a quick question as it seems you use the original head what is the situation with the head shape and what is the new compression ratio sorry thats two questions

john

mossproof · Super Guru

Yup John, same head. As I mentioned in response to Gadget's pic above, the lip at the limit of the 250 bore could maybe do with radiussing a bit to ease the gas flow, but the custom pistons were specced with stock compression ratio, Wossner did the maths off the spec of their standard replacement piston. 10.2:1 IIRC, but don't quote me - it's a long time ago now since I last thought about it! Removing material from the head would thus reduce the CR below stock. Possibly better torque? But I don't think it's necessary.

Gadget the suspense is killing me!

Christos thanks for the carb pic. Presume the throttle cable clears the frame above ok. I think the Mikuni may have clearance issues according to the info on the Aus website. It's all a bit tight in there!

Gadget964 · Veteran Member

I'm super keen too. Hopefully today.

The head work was pretty much only intake and exhaust. Valve seats redone.

Gadget964 · Veteran Member

IT LIVES. Fired straight up.

TTRfan · Super Guru

biggrin biggrin biggrin biggrin biggrin biggrin biggrin

Gadget964 · Veteran Member

First Australian TTR350.

TTRfan · Super Guru

What a cracking bike - looks great! Loving the vintage look biggrin biggrin wink

mossproof · Super Guru

Number five is alive! Good work Mark.

Kaos · Senior Member

Looks great be interested in the ride report

Gadget964 · Veteran Member

Waiting on a few parts. Pivot pegz and Speedo drive are the main bits.
Speedo was posted 2 weeks ago, in Australia, and still hasn't arrived. Post has been swamped over here apparently, meaning huge delays.

ttr steve · Super Guru

I must admit I am confused???? The bike looks awesome, but its a TT350, where is the TTR350? Or did you put the TTR350 engine in the TT350 frame?

Or have you managed to fit the forks/tank/seat and mudguards from the TT350 to the TTR frame confuse confuse

-- Edited by ttr steve on Sunday 17th of May 2020 11:55:31 PM

Gadget964 · Veteran Member

Good. Happy that people are confused already.

Just to summarise:

1996 TTR250 =>

Fitted with:

Totally TTRs 350 big bore kit
TTR600 Forks and triple clamp
TT250/350 tank, shrouds, race plates, and headlight
TTR250 seat modified to suit tank and shrouds
YZ rear guard from the late 80's

Dlight10 · Newbie

Bike looks great! Love the concept.

When and where is your first ride?

Gadget964 · Veteran Member

My foot pegs arrived today, just waiting on front wheel spacer/speedo drive before I can get it mobile. Hopefully in the next few days. With a bit of luck I will have it registered before the Queens Birthday weekend and head up to the Sunset Desert... My mechaninic is keen to see how it feels as well.

-- Edited by Gadget964 on Monday 18th of May 2020 01:06:32 PM

Christos · Veteran Member

Yes, no problem with the throttle cable...

Gadget964 · Veteran Member

www.facebook.com/groups/467237210053657/permalink/2966397470137606/

tripodtiger · Senior Member

That's great Gadget. Looks schmick.

Should go schmick too.

Gadget964 · Veteran Member

I gave the 350 a bit of a local run this morning to get everything settled in. The motor is exceptionally quiet with no weird noises at all. With standard 250 carb settings, it runs surprisingly well--but it definitely needs adjusting. Rich in the bottom, feels OK up to 80kph, then feels a bit restricted after that.... I didn't play with adjusting any of that in this run as I just wanted to get some time on the motor. Plus I should find out next week when my Mikuni arrives, so I'm not going to spend too much time on a carby that's coming off anyway.

As I did a complete bike build, I have also had to re-adjust the new chain, head stem bearing tension and handlebar position.. An interesting point about the TTR 600 forks- I have somehow ended up with 30mm more ground clearance than my sons TTR (which has DRZ400 forks)

mossproof · Super Guru

First mud!
Bike looks fantastic. Somehow looks leaner than the old tt, despite the use of the plastics. Maybe it's the height?
I think the ttr engine is quite tolerant of rich settings. Looking forward to hearing how the Mikuni goes.
Good work,
Simon.

ttr steve · Super Guru

Looks meaner you mean!

Flipping good job Mark, why change the forks? did the ttr axle fit or you had to make a modification?

Gadget964 · Veteran Member

Ended up with full TTR 600 front end- triples, forks, axle, spacers, wheel, brakes, speedo drive.

It'll end up with a better set up for the desert riding that I do, and more adjustable than the 250 forks if I change where/how I ride.

-- Edited by Gadget964 on Saturday 23rd of May 2020 07:03:25 PM