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

Christos · Veteran Member

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

TTRfan · Super Guru

mossproof wrote:
Glad to see there's still some material around the metal ring! I want to speak to the loctite rep about suitable sealants to "help" the base gasket, which I think is going to be quite skinny.
Simon.

I have come to the point where my 350 piston is fitted and the barrel cleaned, sprayed, and ready to fit. What sealant do you advise for the base gasket please? I have blue Hylomar on the shelf but would normally just grease the gasket - old school I know wink

Brian

PS I can't find the thread where we built your 350 engine Steve - can you give us a clue a to its wherabouts please?

ttr steve · Super Guru

page 3

https://ttr250.activeboard.com/t62869904/350cc-big-bore-kit-for-the-ttr250-updates-and-gossip/?page=3&sort=oldestFirst

Gadget964 · Veteran Member

The guys that originally did my dyno are giving me a bit of static about doing successive runs with different set ups--a lot of 'reasons' but my interpretation is "We don't want you in the workshop". So I'm now looking for someone that will let me do the changes myself, and get them to come back for each run.

While there's a delay, I played around with a few different mufflers over the last few days: Webbys, Aussie, and original (short) Staintune. They were mainly just short runs, but working through full rev range and all gears. Seat of the pants feel, with the current tuning and three different riders, the Aussie muffler came out on top, followed by Webbys, then Staintune. There may still be some tuning improvement to be made, which may change my mind on which pipe I prefer.... The Staintune pipe highlighted a slight hesitation at 3/4 throttle.

On the track I decided to run a ride logging program that my son use for training. Although the bike felt good, it topped out at 114kph with 14:48 gearing... Which meant that my son on his Yzf250 desert racer blew past me at a cool 135kph. I'm sure that my gearing is playing a large part, but ouch.

Just to be sure that I'd tried everything, I changed the header back to original as well - no noticeable difference in top speed. I'll get the dyno done with both to check.

My clutch is occasionally slipping as well--new one coming.

Kaos · Senior Member

Hey Gadget, re your clutch if its been rebuilt I reckon heavier springs might sort it out. Re the header pipe the shorty should be stronger and be better for top speed at least thats my experience. I have been using a privately owned dyno in Bendigo, the owner is a Yamaha enthusiast. (Its not a bike shop) I've just put a 36mm Keihin PWK biggrin biggrin on my TTR so its waiting for a dyno run on it I could see if we could get you on as well? I'll let you know but could ber a couple of weeks

Gadget964 · Veteran Member

Is he out at Strathfieldsaye? Long driveway? I used him for my Safari bike... he was the alternative that came to mind. Can you send me his contact details please?

Kaos · Senior Member

No not Strathfieldsaye in Bendigo, I'll message you.

Padowan · Senior Member

So after almost 2 years of having had the kit in my possession, all my other bike projects are complete, the garage had been refloored and were in lockdown, so it seems like its now the right time to start on the 350 project!

Wish me luck!

TTRfan · Super Guru

Good luck Simon!

Are you using the existing engine or are you working on a spare?

Waiting on an MOT to start using my 350 properly.

Brian

Padowan · Senior Member

Will be using the existing engine, don't have a spare. It's out already!

ttr steve · Super Guru

Ye ha! Lots of pics please matey! Can't believe it has been nearly 2 years, where has that time gone 😳

mossproof · Super Guru

Good luck Simon!
Don't forget: Take out the inlet tract bung, and fill the tank with PETROL before the first startup

ttr steve · Super Guru

mossproof wrote:
Good luck Simon!
Don't forget: Take out the inlet tract bung, and fill the tank with PETROL before the first startup

Ooosh!

Yes petrol!

mossproof · Super Guru

And give the bore a thorough clean and reoil to remove any residual honing material.

TTRfan · Super Guru

Padowan wrote:
Will be using the existing engine, don't have a spare. It's out already!

I usually forget to drain the oil before taking the engine out and it's then a right faff to do it - especially if you forget the oil is still in there and take a side case off disbelief

Regarding Moss's advice, I was told to give the barrel a final scrub in warm soapy water.

Padowan · Senior Member

Yeah, I dumped the oil and also removed the sprocket before taking the engine out of the frame, those were the 2 things I thought would be a ball ache if I forgot.

dlee22 · Senior Member

I went out for the first (proper) time on the 350 since Simon was kind enough to take a look at the bike. I have got to say he did a great job with the bike, it feels great to ride and was a pleasure to meet him and take a nose around his 325/350, he's got so many good ideas!

The lanes were really boggy with some "puddles" reaching close to the seat in places!

Not many interesting photos sadly

Gadget964 · Veteran Member

New clutch fibres, plates and springs fitted yesterday. The plates actually looked to be in pretty good condition, but the springs were a bit below spec...

The bike has now been re-fitted with the same gearing and tyre that were used on the original dyno; so it's ready to go.

I'm looking forward to spending a bit of time with Kaos and his dyno mate... and finally getting some figures in. (I've seen what Kaos has done to his TT350, so it will be interesting to compare his TT350 to the TTR350)

Stay tuned.

Kaos · Senior Member

Good work Gadget, we are still waiting on the dyno being rebuilt into that container. BTW, You gotta beat (TT350) 29.1 HP biggrin (at only 5021rpm! just above idle! biggrin ) and 45.5 nm at 4500 rpm. Its a tractor!!!. Going to run the TTR263 up as well with the new 36 mm Keihin it has picked up plenty of high end power from its previous 23hp. Revs out like a modern bike now. I reckon that might pull similar HP but hasn't got the torque.

Gadget964 · Veteran Member

It would be interesting to see how much the final drive ratio affects the curve. I'm sticking with 14:44 to get the comparison with the first run.

Kaos · Senior Member

I think they program all the primary drive ratios, gearing etc into the dyno program

mossproof · Super Guru

Latest batch of barrels now done. I will get them down to Steve for the shop ASAP.

Looking forward to your results Gadget. Interesting seeing the results of the carb swap.

Gadget964 · Veteran Member

Dyno finally scheduled for next Wednesday..

ttr steve · Super Guru

6 barrels here, 2 sold, 3 i am dealing with, that leaves 1 available, get in

Quick for a Christmas present to yourself

-- Edited by ttr steve on Thursday 10th of December 2020 08:34:51 AM

Gadget964 · Veteran Member

Ok, so that was a big day: I finally managed to get to a dyno - huge thanks to Kaos for hooking me up with Alan.

Multiple runs (I brought home 15 print outs, but we did more runs than that). Initially the Mukini was too lean off the pilot, and too rich on the main.... and I thought that I was pretty close! Ended up going from a 137.5 main down to 130, then further to 127.5. Needle changed to 3rd clip from the top (was 2nd). The pilot was also increased (I didn't actually find out the size- just put it in when it was handed to me).

Outside temp: 32 deg C.
Humidity would have to be somewhere around 40%
Elevation above sea level: about 250m

Webbys Shorty header.
Final drive 14:44

Best run once tuned:
21.71349 kw @ 7301rpm (29.18 Hp)
30.06 NM @ 5947rpm (interestingly, the torque 'curve' is reasonable flat between 4500-7000rpm, which will suit my riding style)

Muffler preference: Staintune had very marginal gains over the Webbys through most of the range, but Webbys power continued further into the rev range (I saw it hit 9700 a few times today). Torque was down in the Aussie compared to the others. At the end of the day, I'll probably still run the Webbys.

mossproof · Super Guru

So does that beat Kaos' TT350, or is it just that you have gone to an extra decimal point

Of course, rounding up it is 29.2hp. Good result anyway.
The torque curve is definitely the best feature I think - so flat, makes it really rideable without masses of gear lever action.
How do those jets compare with what they recommend for a standard 250?

Gadget964 · Veteran Member

I thought that I saw a 29.6 on one of the early runs, but that was an anomaly before we started smoothing out the AFR. Once dialled, it was consistent 28.8 to 28.9 with Aussie, then a bit higher with the others, with an earlier hit on the torque curve.

The jetting was very close to what Mikuni Oz sent the carb to me with... Up a size on the pilot. When the weather changes it may be a different story though.

Gadget964 · Veteran Member

I also forgot to mention that the pumper was disabled for these tuning runs.

Kaos · Senior Member

And I noticed it was running consistantly cooler than my both my TTR263 and TT350, maybe be the bigger barrell with more surface area on the fins cools better.?

Kaos · Senior Member

mossproof wrote:
So does that beat Kaos' TT350, or is it just that you have gone to an extra decimal point Of course, rounding up it is 29.2hp. Good result anyway.
The torque curve is definitely the best feature I think - so flat, makes it really rideable without masses of gear lever action.
How do those jets compare with what they recommend for a standard 250?

Moosproof

Yep Gadgets bike beat my TT350 in KW but it was close , 21.71 v 21.67 KW (29 ish HP) both have head work and fancy exhausts upgraded carbs.

But the TT350 is massive in torque, surprised everyone, including some built TT500 owners, 45NM at 4320 rpm, over 37 NM from 3000 rpm onwards to 6200 rpm where it starts to drop off.

And for reference my TTR263 cc pulled 19.05 kw (25.55 HP @ 9350 rpm and made 23.07 NM @ 6961 rpm. All on the same dyno different days weather etc.

Kaos · Senior Member

Mossproof,
What compression ratio is the 350 kit running?

mossproof · Super Guru

Yep that TT350 is a stump puller by the sound of it!

Compression ratio should be more or less stock (10ish?) I asked Wossner to do the calcs for me and they just produced an 86mm piston based on their 250 piston with some shaved off the top, judging by the shape of the valve reliefs.

Remember the ttr conrod is smaller top and bottom than the xt/tt, so I didn't want to go all-out for a high performance competition spec. The aim was for a tractable torquey trail bike, and to my suprise and amazement it seemed to work

Nice to hear it runs reasonably cool too. Overall dimensions of the barrel are similar to standard, but the fins are a bit thicker.

Christos · Veteran Member

Hi guys! Is a breather modification needed for the 350? Bigger hose or anything else? Internal diameter please?

-- Edited by Christos on Monday 8th of February 2021 07:14:22 PM

mossproof · Super Guru

They definitely breathe more heavily than a 250, leaving more oil in the cyclone separator. If you have a 4GY engine with the crankcase breather behind the starter motor, getting a later type cam cover, or modifying the existing one with a breather outlet, helps reduce the oil mist getting ejected, but I have not found a perfect solution yet. Using both breather tubes, and a larger cyclone would be good, but I haven't had the pipe blow off from excess pressure.

If Kaos is reading, how big is the crankcase breather on the TT350?

Kaos · Senior Member

mossproof wrote:
They definitely breathe more heavily than a 250, leaving more oil in the cyclone separator. If you have a 4GY engine with the crankcase breather behind the starter motor, getting a later type cam cover, or modifying the existing one with a breather outlet, helps reduce the oil mist getting ejected, but I have not found a perfect solution yet. Using both breather tubes, and a larger cyclone would be good, but I haven't had the pipe blow off from excess pressure.

If Kaos is reading, how big is the crankcase breather on the TT350?

On the TT350 vent hose is:- OD 18mm ID 16 MM, and down on the crankcases

Christos · Veteran Member

I have a 4GY engine but the breather comes from the cam cover. I think the ID of the 250 hose is about 10 mm maybe?

TTRfan · Super Guru

It is something I have thought about. The later crankcases have a plug fitted in the breather hole so I don't think it would be hard to knock it out and put in some sort of adaptor.

Gadget964 · Veteran Member

The group has been quiet for a while...

Looks like my 350 will be undertaking a fairly big test- My son is planning on racing it in the 24 Hour Reliability Trial in July.

The 24 is a unique event run in South Australia, in the middle of winter (regularly sub zero temperatures and/or rain). The riders circulate a (roughly) 230km/6 hour loop, with timed off road sections linked by road transports..... Four times.

No pony express, no service crews or pits. If you don't start with it on you, you can't use it (tools, tubes etc.) there are exceptions for fuel and food. One rider, one bike for literally 24 hours.

We just have to sort the lighting out, and tune it for cold weather

MXTV Feature - The Swann Insurance SA 24 Hour Trial - YouTube

-- Edited by Gadget964 on Friday 9th of April 2021 09:04:02 AM

TTRfan · Super Guru

Gadget964 wrote:
The group has been quiet for a while...

Hi Mark - yes - all quiet here but I did manage to get out for my first trail ride on the 350 a couple of weeks ago wink

Nothing remarkable to report. The bike started and restarted well when hot and pulled like a train! Hope to ride more now our UK Covid restrictions have been relaxed biggrin

Best wishes to your son on his big adventure! Hope it all goes well and looking forward to hearing how it goes.

Brian

Gadget964 · Veteran Member

It's now official. My TTR350 will be racing the 24 Hour Reliability Trial in July (middle of winter for us- more details about the event a few posts ago).

I'll be leaving the bike in the hands of my son for the event... he can ride a lot better than I ever could (image below- his first ride on the 350).

Kaos · Senior Member

Hey Mark
That will be a good test of the bike.
Is that the week straight after Hattah. Is Liam doing Hattah as well, two of the toughest Australian races back to back.
Oh to be young again.

Gadget964 · Veteran Member

Yes he is. Hattah Desert Race one week on his YZF250, 24 Hour Reliability Trial the following weekend.

I'm keen to see how the 350 goes. First one to be raced???? Now that I have the lighting sorted, I'll get the bike out to check the cold weather tuning.

I know that the TTR is capable of a good result (I had a class win on one in 2006), and that Liam has the ability, as well as familiarity with the TTRs as he used to own one.

ttr steve · Super Guru

Awesome Mark

Looking forward to hearing the results and hoping Liam leaves all in his dust!

TTRfan · Super Guru

Good luck to Liam! biggrin biggrin

mossproof · Super Guru

Good luck ttr 3 fiddy too!
Nerve wracking for me as primary development engineer. I'm glad of your dyno runs to make sure it's tuned properly.
Best of luck!

TerryK · Super Guru

Gadget964 wrote:

It's now official. My TTR350 will be racing the 24 Hour Reliability Trial in July (middle of winter for us- more details about the event a few posts ago).

I'll be leaving the bike in the hands of my son for the event... he can ride a lot better than I ever could (image below- his first ride on the 350).

Are you coming over for the 24hr in South Australia ?

Good luck, it is the coldest weekend of the year, my mate does one of the controls

Is he doing the full 24hr or the rally class of two laps (1st & last lap in the daylight)

Cheers Terry

Gadget964 · Veteran Member

The initial dyno work was done at just over 30 degrees c, without the pumper connected. As the 24 Hr Trial will be running through towns, on and off, all night- I also changed to the Staintune muffler with the quiet insert (94db). When I got it out a few days ago, the bike was flat just off idle . In the Mikuni TM33 I ended up with:

2 turns out on the air screw,
127.5 main,
25 pilot,
Needle on the middle clip.
Unifilter O2 Rush air filter at the moment (I'll also be testing with Unifilter dual stage.)
Original snorkel trimmed, airbox lid sealed.

I know that there would be gains in opening the box a bit more, but the Reliability trial is renowned for either having significant bulldust, or being wet. The bigger gain will be not having to change the air filter as often. (In 2006 when I raced, with a much more open airbox, I had to do 9 -yes, nine- filter changes to keep the bike running right.)

Gadget964 · Veteran Member

Hi Terry,
I'll be there as well... Due to the strict "Do it yourself rule" for the riders, I will be there for support, guidance, and filming only.

He's entered the main event. What control will your mate be at?

I'm heading to Mildura with the bike some time this week to dial in the bike to Liams needs. Interesting thing in this years regs: Scruitineering the night before, bike locked in park ferme... not to be started until 1 minute before allocated departure time.

TerryK · Super Guru

Gadget964 wrote:
Hi Terry,
I'll be there as well... Due to the strict "Do it yourself rule" for the riders, I will be there for support, guidance, and filming only.

He's entered the main event. What control will your mate be at?

I'm heading to Mildura with the bike some time this week to dial in the bike to Liams needs. Interesting thing in this years regs: Scruitineering the night before, bike locked in park ferme... not to be started until 1 minute before allocated departure time.

Don't know what control yet, he's with the BSA club, he also has a TTR, WRR & Triumph Scrambler like me

Cheers Terry

Gadget964 · Veteran Member

Just over a week to go until my 350 starts its first race.

Liam has a lot of confidence when riding this bike since playing with the suspension a little, and adjusting the ergonomics. We both find the bike much better to ride with my steg pegs on-even though it makes air filter access more time consuming. But we are running with the theory that he'll be riding the bike for 24 hours, but may not have to change an air filter... So stegs will have greater gain. Due to the nature of the race, we also changed the gearing from 14:44 to 13:44, but it'll still do 120kph.

The motor itself has just over 30 hours of use, and remains extremely smooth and torquey, so we have no concerns there.

We have a little more testing to do with another light, but are pretty happy with the set up. Other than that-fresh oil and tyres to be be fitted early next week... once the Hattah Desert Race is over.

With a bit of luck, Covid restrictions won't impact our ability to get there (several riders have been denied entry to the state due to border closures. If the current regulations continue as-is, Liam may be the only interstate competitor)