I had an 88 model. These are the things I remember about TT350s in our part of the world:
Changes over the years: To my knowledge, the TTs sold in Australasia did not change spec throughout their run, apart from BNG.
Outright Power: A bit more peak than any stock XR250, but the TT350 has much more low-end grunt and tractability. The 25/26mm twin barrel slide/CV hybrid carb works really well when set up properly. The six speed box has a great spread of ratios for trail riding.
Weight: In registerable form, rated at 113KG dry, putting it somewhere between current XR250s and XR400s.
Suspension: Very soft and plush. Softer than an XR so for any serious work, needs springing and damping help here.
Handling: Has slower stable steering and feels longer than an XR. THe TT is a good bike for climbing technical hillclimbs.
Reliability: An anvil is only slightly more durable than a TT. The chassis and suspension links will wear out long before the engine. No known points of weakness and maintained properly, should last almost forever.
I built a pipe for one of the TT350 engines and it was a real Torquer! Tried to figure out why it wasn't stronger on top and then found out that it had the same sized valves as the XR250 Honda. Could be the same head as is on the 250, but I don't know.
I rode an XT350 as my street bike for a while. It has the same engine. I was able to coax a little more power out of it by eliminating the resiriction in the airbox and muffler. The airbox was the real power limiter, at least on the street version. I had to rejet slightly. The bike would go about 88 MPH indicated with me in a full tuck.
I really enjoyed the bike and would have kept it if the suspension were better. I guess the TT has far better suspenders than the XT.
i was told that the tt350 and the tt250 were the same as each other except for the barrell (same frame , same bottom end ) does any one know if this is true or not?
It may be partially true. The piston is much larger on the 350 so I would expect the cylinder head to be sized properly. However I never took the engine apart to see. My 350 would rev to about 9K before running out of power. I suspect the head was not the 250 head due to the way the bike ran.
Better running is equal to porting, bigger carbs, cam, os valves IF they will fit, higher compression and a larger perfoemance tuned exhaust. The exhaust ports are "MICRO" sized and nothing like a typical 350 Honda of the same period. MUCH less than a typical 400 factory port of today.
Swiss, while that may be true about exhaust port size, the Honda's typicallly have a bigger port and then force the exhaust into a small headpipe. So the port size is roughly and effectivly the same! In casual riding with my neighbors XL350 Honda, the Yamaha is a tick faster all around.
The pipes aren't really any good on either the Yam or the Honda. Both are too small and poorly tuned. Both can be improved a LOT. The Honda can handle a 40mm carb, when used with a hc piston, porting and one of the mild cams that are available. Also 1 1/4" head pipes joining into a 1 3/4" collector and then a meg. will help both engines. I was told a long time ago that the XT/TT350 MAY be able to use the XT550 carbs. Porting would help the 350 a bunch, along with some os valves if they will fit. Basically, the 350s are nice play-bike engines, and don't make any serious performance. Years ago, I built similar complete exhaust systems for both of the engines at the same time and the Honda with the larger valves would rev out strong. The Yam would pull the front wheel up with a simple twist of the throttle, but flattened out in the upper rpms. We continued to modify the Honda, but the Yamaha owner didn't want to pay the bucks to get more. This was in the early '90s.
I am the original owner of a 1986 TT350 and still ride it today. The bike I have has had no reliability issues at all. Grease the bearings, adjust the valves every 5 years (really has only needed an actuall adjustment after break in) change the Air filter to a K&N, and if you want a bit more oomph Cobra makes a spark arrestor for it for around $150.
With age the rubber on the intake manifolds cracks and causes air leaks. If you buy one plan on spending $100 for new manifolds and o-rings.
In 1986 the TT overshadowed the XR 350 and took the reigns as the 350 to beat. It was the best until Suzuki brought out their DR 350 which had slightly more in the power department and a slightly better chassis.
Suspension is the limiting factor on this bike. Whoops upset this bike very easily if you are not a good rider but on the tight trail it feels small and agile. The front end pushes in fast corners so front tire choice is critical. Being of the old enduro design the bike has a dip in the seat and encourages sitting on it's comfortable couch. Transitions from sitting to standing are not the easiest.
With all that said I will never sell the bike because it will never die and it grows on me. I have used it in the desert, on Forest trails , I dualsported it through college, and rode the ISDE qualifier in Idaho City on it this year (until an evil log took out my knee for a few days). It is as fast as a CR 500 in the tight stuff (I had one, I know), Can climb any hill (may be in first at the end but it will make it), and is forgiving for a beginner rider. I think everyone needs one for a back-up/play bike. After all you can find one for a few hundred.
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