First Model TT350??

[Colin Jay]

Sorry, No. I might be looking for one myself, as I have just measured the bore on the cylinder that I have and it is 4th OS and the corrosion would require a rebore to remove.

that's ok ive managed to get a cylinder on standard bore and needs to go to 1st oversize
yep mines on 4th and its worn, but when looking I found the std twin came bore is 73mm
and the std single came bore is 75mm so does anyone know if the single cam piston can go into the twincam if anyone has an old sohc piston I would be interested in it to do a comparison

The SOHC piston has a higher deck height (distance from piston pin to piston crown) and domed piston crown, and also uses a larger diameter piston pin.


SOHC piston on the left, DOHC piston on the right. (SOHC piston also has a large hole in the top due to a dropped valve!)

As the crank in my engine (TT250) was stuffed, I have gotten hold of a XT250 bottom end which is virtually the same (yes, I know some of the gearbox ratios are different) and will be building up this engine with the TT250 head. I was also able to find an XT cylinder that is 0.5mm oversize to replace the rusted 4th over cylinde I have. Pistons in this size (0.5mm OS) are NLA from Yamaha, but I was able to get one from Halpins in QLD.

Frame and assorted parts are in being powder coated and hopefully will be ready next week.

If the Big Race tomorrow turns in to the Boring Race, I might even get the engine together tomorrow.

[shelpi]

Sorry, No. I might be looking for one myself, as I have just measured the bore on the cylinder that I have and it is 4th OS and the corrosion would require a rebore to remove.

that's ok ive managed to get a cylinder on standard bore and needs to go to 1st oversize
yep mines on 4th and its worn, but when looking I found the std twin came bore is 73mm
and the std single came bore is 75mm so does anyone know if the single cam piston can go into the twincam if anyone has an old sohc piston I would be interested in it to do a comparison

thank you for doing that and for the other info as well

The SOHC piston has a higher deck height (distance from piston pin to piston crown) and domed piston crown, and also uses a larger diameter piston pin.


SOHC piston on the left, DOHC piston on the right. (SOHC piston also has a large hole in the top due to a dropped valve!)

As the crank in my engine (TT250) was stuffed, I have gotten hold of a XT250 bottom end which is virtually the same (yes, I know some of the gearbox ratios are different) and will be building up this engine with the TT250 head. I was also able to find an XT cylinder that is 0.5mm oversize to replace the rusted 4th over cylinde I have. Pistons in this size (0.5mm OS) are NLA from Yamaha, but I was able to get one from Halpins in QLD.

Frame and assorted parts are in being powder coated and hopefully will be ready next week.

If the Big Race tomorrow turns in to the Boring Race, I might even get the engine together tomorrow.

[Tomthesparky]

 If your still going with the TT350 engine i recommend hanging onto the 250 head, the valves are the same size (on the ones i have measured) but the smaller combustion chamber helps lift the compression by a fair bit. You will have to weld up the existing 250 oil gallery between the combustion chamber and the cam chain tunnel and use the 350 external oil line. I have done this mod and it livens the old girl up a bit, no problem with pinging or overheating although i did weld larger fins onto the head (not sure if this helps or not). Pay attention to the squish band when putting it back together as from the factory they can be pretty loose in tolerance here, I ended up dropping off the base gasket and running case sealant to get it about right.
 They also run stupid lean on the pilot jet if still on factory jets, jets can be hard to come by in different sizes but i have found that the pilot jet from the XT350 is pretty much bang on. the primary main and secondary main are standard. this is on a bike with larger headers opened up airbox and a staintune exhaust.
 Hope that helps

Tom

[Mick D]

Pretty helpful first post Tom kinda makes me want to get a tt350 project  
What else are you into in bikes?
And what state are you from?

Welcome aboard.


Cheers,Mick.

[Tomthesparky]

Thanks Mick,

Forgot to mention that the best money is spent on the suspension, had the shock revalved resprung to suit my weight- factor in a re-chrome of the shaft as they all seem to eat themselves. forks much of the same with cartridge emulators. Hands down the best thing done to the bike, very happy to recommend the business that did the shock

From NSW, Maitland area. Also have a 86 kdx200 and and 81 katana1100.

As for a project bike with a few mods they go pretty well, can hold my mates on wr450's in the tight to med scrub, only lose out in the open. And at least i don't have radiators to wreck my day when i bin it

[Mick D]

 

Great place Maitland, I lived/slept up there on and off for Seven years, country folk are cool.

Just last week a new acquaintance was telling me a similar story about these modern suspension techniques and outcomes on his old Maicos. A brand that had close to the best handling suspension in the day, but made even heaps better by his account?
So starting to accept the reality of these mods, after just reading your account of it too

NEXT: THis is an example of what we call a thread hi-jack

You have well suited bikes there for NSW Vintage Trail Riders club, heaps of fun.
http://forum.ozvmx.com/index.php?topic=37135.0

If you want to feel the buzz in your own back yard?
Great week end coming up on the 5th and 6th November at Cessnock
Drop in for a look Cost to you will be nill, unless you choose to purchase from the local clubs Kitchen

[FourstrokeForever]

Hey thanks for the excellent write up on the TT mods Tom. I have done similar mods to mine apart from the 250 head. I took 20 thou of the head and barrel to bump up the compression a bit. I figure I have 9.8:1 now which is better than the standard 9:1.
I suspected my TT was (is) running lean. I drilled the original pilot jet and lifted the needle which has made it better but it's far from acceptable for me. What size is the XT pilot jet?

[shelpi]

Yay me jug arrived and yep on std bore and yes will need to go to 1st o/s
thank you for your insight, you have my attention
Oh yer who knows the best place to source the dohc pistons, a bit thin on the ground plus I'm a tight ass

[rocketfrog]

A bloke I work with has a 1993 ish TT350 which will not start and needs air scoops and side covers (missing somewhere along the line) also has a bunch of older TT350 stuff going with it, mostly frame and susp stuff from what I see.

Any how, he wants to clear space in his shed and has no interest in this bike or parts. I suppose you can buy a going bike most days of the week for around a grundy and he asked me what I thought is was worth as is, maybe half a ton?

If any one reading this thread is inspired to own a TT350 and they want to tinker with it you can send me a pm for Gavins contact details and you might hash out a deal on the TT.

The bike is located in between Ipswich and Toowoomba and would be a pick up arrangement only.

Just putting it out there, the bike is not advertised anywhere and it needs a new home.

[Tomthesparky]

The standard TT350 pilot is a 40 the xt350 pilot is a 42, cannot remember if i reamed it a touch o/size from that. Mucked with the pilot until i had the needle screw 11/2 turns out and it is clean off the bottom. Watch the cam cap retaining threads or better yet replace the bolts with studs as the threads in M6 threads in the head seem to be pretty soft and prone to stripping out. Also keep the automatic de-compressor, as yamaha made the kickstart shaft out a special steel/cheese alloy that is pretty easy to snap the splines off

[Colin Jay]

Thanks for the advice on mod' ing the 350 engine. At present I have decided to rebuild a 250 engine using a XT bottom end (yes I know the gear ratios are different to the TT) and fit the TT head an carbies.

I have actually gone a bit over the top considering this was supposed to be a quick and dirt rebuild to get a better bike for next years SART series. I have had the frame and ancillary fittings powder coated and all the bolts axles etc re-zinced. Since the frame looks so nice I have lashed out and ordered new front and rear guards as the one I have were going to look tatty along side the new Clark fuel tank that I will be using.

I have just finished a strip and clean of the front forks and am looking at getting the rear shock overhauled. I have struck a minor problem with the forks as I only have a XT manual, and need to know the fork oil capacity / level, also a suggestion of what weight oil is best in the forks as there are std would be helpful.

[FourstrokeForever]

Oh yer who knows the best place to source the dohc pistons, a bit thin on the ground plus I'm a tight ass

I got a wiseco from ebay.....you need to search the US ebay site

[80-85 husky]

a good start point is 150 mm from the top of the tubes with the forks collapsed using 10 wt but im sure someone will pop up with the correct details soon

[LWC82PE]

I think i will have specs on the fork oil. Will report back in a couple days when i find the book. Also in USA they were called a TT225.

[shelpi]

Oh yer who knows the best place to source the dohc pistons, a bit thin on the ground plus I'm a tight ass

I got a wiseco from ebay.....you need to search the US ebay site

thank you