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tt350 hotstart and idle issues

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Hi guys just wanted to know what you guys think the problem could be for a tt350 I’m working on.

I’ve been doing a dirty get it going job on a tt350 it’s not what i like to do but it’s all I’m allowed to do on this one (it’s a pity) I’m working on getting ownership of this bike but that’s another story.


The problem I’m having is that the bike will not idle when it gets hot or well when its cold. Even if I turn the throttle stop screw in as far as I can the bike will idle then die on me. The idle fuel screw on the carbie does not seem to make any change to the Rpm of the bike at idle no matter how far I turn it in or out?  There is also a unconfirmed hot starting issue on this bike that it becomes impossible to kick after it gets ridden a few Km’s, I cannot confirm this as my friend test road it when I was away and said this was a problem but when I checked the bike there was no fuel in the tank? This could be due to the small leak on the petcock between when he road and I checked as iv been OS for two weeks so I have to check this out again.


As for how much compression it has I’m not sure really as I’ve never see one of these in good condition or ridden one I’m going to order a tester so I can get some numbers, but I think it would be 60 to 80% of original and if I owned it I would do the top end. As for engine noise it’s really hard to tell if there are any bad sounds as someone during the life of this bike has removed the insides of the exhaust I have to put hearing protection on just to work on the thing but no obvious bad sounds. This bike blows some smoke but is not terrible for its age looks to me like oil smoke from the top end.


The Work I’ve done so far:

  • Cleaned the carbie, air box, intake tubes, and intake boots.
  • Resealed intake tubes to back of air box with liquid gasket (have to check for leak here any suggestions on how to do this?)
  • New Hiflo brand air filter, oiled with air filter oil. (Could not get Yamaha original in town annoyingly)
  • Reglued the left intake boot back on to its metal foot and resealed with liquid gasket. (used a special high temp epoxy to bond the boot back on to the metal foot it’s not going any place soon)
  • Pressure cleaned fuel tank ( looked like a Pterodactyl had taken a dump in it)
  • Cleaned petcock inside and filters (replacement is on the way as this one leaks a little)
  • Removed 300ml of oil from the bike as it was massively over filled. This oil was in ok condition with no signs of fuel or water contamination, a small amount of metallic contamination was present in the oil. Confirms to me that a top end rebuild is needed in this bike, likely a rebore is going to be needed but I’m guessing and that is way beyond the scope of what im alowed to do on this one. untill i can get ownership that is.



Any Ideas guys? i need another opinion on this one. What direction should i be looking in?

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When you had the carbs apart for cleaning, did you verify that they still contained the stock jets?


With the way you described the inside of the tank when you cleaned it, I would suspect that a lot of that gunk had made it into the carbs and really gummed up the works.  If the owner had been fiddling with the jetting to get it to run (possibly richening it up), and to mask the potential air leaks that you found around the intake boots, then that poor thing could be basically flooding out when it is running.

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Iv had a think about it and i think i have stock jets a 40 pilot a 122 and a 125. Iv got to do the decomp seal so im going to have to pull it down again so i will check it out.

Im thinking iv got a air leak someplace but im away for work for another week so ill check out the jets when i get back.

Any ideas on trsting for air leaks?

Cheers for the imput.

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Most common location for an airleak on the TT350/600 is the intake boots.  They are metal and rubber, and the glue that holds the two materials together doesn't last forever.  So you will often times find an airleak at the glue joints.  That and the rubber part of the boot will eventually dry out and start to crack.

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