tt600 runs,dies, then wont start
 

hi i have a 86 yamaha tt600 that runs like a bat out of h*** but if you let it idle or come down to an idle it usual stalls after you have been riding about 10-15 minits weather you ride it hard or just let it idle.the main problem is when it does stall you have to wait about 15 minits before you can start it and it starts in 1 or 2 kicks. when i pull the spark plug it is sooty,carburetor is still cold,still has very good compression,and piston is not stuck in the bore.

i have been working on this for a couple weeks and every thing that i see is saying it is too rich like sooty plug after stall and black smoke at and just off idle. but every thing i read about jetting a bike carb says the piolet jet is too lean.

i will try almost anything except buy new carbs

check the valve clearances thats a comon prob for hot starting
sooty plug is def running rich have you checked the air filter is clean that will make it run rich and can make it stall

Have you taken out the carburetors out and looked inside?

Your problem might be a dirty carb. If you have the time and experience just take out the carb, open them up and give em a thorough cleaning. I use break cleaner for that kind of thing, but there are specialized cleaners for carburetors available.

If you can't be bothered, there's also fuel additives available which are supposed to clean the carb while running the machine. Worked for me once but I would not count on it.

ok i will check the valves again, the air filters are new and not over oiled
both carbs are spotless in side.used 3 cans of carb cleaner 2 weeks ago

I think you need to take your jets out and check what they are ?

Then get it all back to standard jetting with the needle on the right slot and the pilot screw set to default (2.5 turns I think - please check).

Then as long as your filter is clean, you should have a good base to start with.

Also it could be that its running really rich on the pilot screw/jet so it will only run at full throttle (lots of air getting in).

Personally I think its your pilot circuit or perhaps the vacumn could be sticking open. Did you check the diaphram and that the plunger falls again ??

Your valves and compression seem to be ok if it fulls full strengh at full throttle.

ok i know both of the main jets are are a #52 drill bit(.0635)
and i had to move the needles up 1 notch to get ride of the bog
and drilled out the main jets to get some more fuel.
the piolet jet says the right size on it

the reason for the change is i have 2 2inch x 4inch uni filters,bored it .040 larger and bumped it to 12:1 cr,and opened up the exhaust

go back to standard jet sizes then do a plug check a .40 oversize even with a high comp piston wont need a big jet change probably just up one size

the over sized piston didnt need much more fuel it was the fact that i am now using 2 air filters that flow more than the single filter that was on their and i opened up the exhaust so i can get more air in and out of the engine.
and as of right now it is running with an air fuel ratio of 13.5-14 to 1 so it actually wants a little more fuel at higher rpm's

what do you mean by opening up the exhaust have done any head work cams? porting?

i cut the back of the muffler open and made it into a home made straight threw glass pack muffler welded it up a little grinding and you cant even tell.
as for cam,porting not yet waiting until next winter

the home made exhaust job will compromise things like the carburation,
a large increase in exhaust flow needs to be balanced with the induction system basicly bigger carbs

i know what you are thinking. that i went to a giant exhaust but it is basically like buying a performance exhaust and bolting it on.mine is basically like a aftermarket performance muffler but stealthy. think fmf muffler inside a big stock muffler

if what you are are saying is still true then every body that buys a performance muffler needs to buy new carbs?

aftermarket cans are developed in such a way to keep the air flow through them within the capabilities of the induction system the laser pro duro can on my bike even has a baffle in the link pipe to ensure there is the correct back pressure in the system.

yes technically speaking everybody that buys a performance can needs to buy new carbs but as i mentioned above this is taken into account by the r&d work done by exhaust companies.

the holes in the perforated tube inside the can make quite a difference what tube did you use post a pic

http://biggunexhaust.com/popup_image...ID=571&image=0it is the big gun exhust 17inch quiet core. it has a 1.5 inch id
http://biggunexhaust.com/images/b-quiet-core.jpg

looking at that pic i'd say a starting point for jetting would be up 1 size, raise the needle up 1 notch from standard then do a plug chop.
get a couple of genuine jets as just drilling em out is no good the jets are actually tapered (mini venturi's) and some are sized on flow rate not bore size.
i use twin mikuni bcr32's but i've got a 2mm oversize high comp piston full flow exhaust and very high flow air filter set up.

do you know what jets fit a stock Yamaha carb?i couldn't find any

i got one more idea a guy i work with had a problem just like this when the engine got up to temp the stator wasn't putting out as much voltage giving a week spark which caused bad performance,sooty plug when it stalled and would not start after it stalled.

so i looked at alitle more things while riding
first speed i found a spot that i could do some speed runs over and over again first run 55mph every run after that wold go down 2 mph from the previous
used a gps and got top speed

second temp after it stalles the case temp has to hit 150F then it will start 1 kick if it is 120f it will not start at all
did this about ten times