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Post Info TOPIC: 350cc Big Bore Kit for the TTR250 - updates and gossip!


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350cc Big Bore Kit for the TTR250 - updates and gossip!
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Gadget I do not know if this will help, I have a similar setup but not the 350. Short header, after market exhaust and 34mm carb. 52 pilot ( you probably need smaller for the 350), needle all the way up and 165 main.

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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?



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page 3 

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



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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.

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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 biggrinbiggrin 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 



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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?



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

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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!

 

 



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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



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



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

 



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

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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!



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

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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.



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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.

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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



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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.

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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.



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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.

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

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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.

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Dyno finally scheduled for next Wednesday..

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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

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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.



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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?

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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.

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

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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.?

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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.

 

 



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Mossproof,
What compression ratio is the 350 kit running?

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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.





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