TT600 starting issues
 

I know there are many threads on here for this kinda thing but mine is an awkward one..

So TT600 poss '93, kick start.
Been stood 12 years
Carbs cleaned
New fuel.

Kicks and fires on chike but won't tick over for more than 2 seconds.
Can occasionally catch it with some revs but only rev once.

Could do with some help please.

It's not clear if you are idling with the choke on or off, but could it be the engine idle speed?

How well were the carbs cleaned? Could be there are jets still blocked, or less likely fuel filter plugged. I'd give it a new spark plug too, just to be kind ;) and sure. Sounds like fuel issues / dirty carb though.

Have you checked the float level is correct? What colour is the spark plug - black and horrible or clean and white?

check the side stand ignition interlock switch too

Does the stand interlock switch allow the bike to fire but not run?

It only attempts to fire with choke on, I have tried it with various different settings on the idle screw.

I agree with the fuel issue diagnosis. I took the carbs off and fiddled a few times and it seemed to improve a little each time so I sent the carbs to a garage. They didn't have an ultrasonic cleaner but they did soak them and clean them up. They changed the gaskets etc but not the jets. I had previously had the jets out and they were clean as far as I could tell.

I know about float level but have no idea what it should be set to. I'm thinking it needs checking as I fiddled a lot before knowing what I was doing.

in my 600e interlock allows one spark, so it sounds like it "wants" to start


still, could be intermittent contact, so just by pass it to be sure


have you checked you have good fuel flow going into carb?

It fires for a couple of seconds so i don't think the stand switch is at fault but I'll bypass it anyway as I don't have the original stand and the replacement doesn't have the bit that activates the switch.

I don't really know how to check if I've got good fuel flow to the carbs. It fires nearly every time, just won't tick over or rev. As soon as it does I can start it again.

Could be air breather. Try with the fuel cap off.

unscrew the carb bowl drain plug, place a container bellow the carb and open the fuel tap.



you should see a decent constant flow from the hole.


have you tried to simply raise the idle stop adjuster so it revs higher?

Quick and dirty float level setting when you don't know correct is "level".

"Assuming" it's a relatively standard carb with a pair of floats:

In other words turn the carb upside down, hold the floats up with your finger tips, lower till the tab that pushes on the float needle just touches it. The floats should be visibly in some way more or less "level". Bend the tab as need to do that. Ideally of course find a manual with the correct procedure and setting.

Re idle stop adjuster - I'm assuming you use the throttle to try and keep it running, so the throttle stop / idle adjuster shouldn't make any difference.

Re mixture screw - a generic setting to start without a manual for the right setting is about 1 to 1 1/2 turns out from fully in - LIGHTLY seated in - tight just ruins the seat, so gently.

Turboguzzi's comment re unscrew the float bowl etc is excellent - that makes sure fuel is getting all the way to the float bowl. From there it's making sure the carb jets are all clean, and of course correctly assembled, good o-rings etc.

Finally - GET A MANUAL! :) It will make life so much easier. I've been wrenching for over 50 years, and recently bought a new-to-me DRZ400E. It came with a factory service manual, and I bought a Clymer manual as well, as they are often more detailed on procedures. You can't have too much info!

All the advice on settings above is exactly what is suggest. I don't know the Yamaha carb well but I do know the equivalent Kawasaki one. On aKLR650 this happens whenever the bike is left to stand more than a few months and are caused by some of the pilot circuits getting blocked. Simply cleaning the jury is never enough. I suggest you try and clean all the different passages on the carb using an aerosol cleaner - simply put the small borr tube into each opening and make sure it comes out somewhere else. Good luck.

Sent from my moto g(8) plus using Tapatalk

TT600.. These things are a pain in the arse even when they're perfect.

I sold my TT600RE because it literally could not be fixed. It was broken from new. They were thrown together by Yamaha with mis-matched parts and never ran right.

The float height on these bikes is CRUCIAL. They flood very easily and won't start if the level isn't perfect too.

Yours will start with the choke though. HOORAAAHH. Your problems aren't that bad.

I would also follow the advice here and start with your pilot circuit and idle settings.

The bike has been sitting for 12 years. You say you cleaned the carb. I've read a MILLION threads and had a thousand customers who say "I've cleaned the carb and it still won't run".

You haven't cleaned a carb unless you've stripped it down to it's individual components. Every air way, fuel way, o-ring and spring. Ideally you want to soak it in solvent in an ultra-sonic bath and then use compressed air with a fine adaptor to blow out all the passages. Then you want new o-rings, new gaskets and then set up the carb to the factory settings.

My advice is to get some brake cleaner or 'Power start and spray a very fine mix into the air box and kick start it. If the electrics and compression are fine then it will burst into life and rev it's tits off for as long as you keep spraying. Don't do this for more than a few seconds though.

It is totally possible that your problems are electronic too. Do you have a strong and consistent spark ?

Ted
MotoRevive.

OK bit of an update....

Went to try again and the fuel overflow pissed out fuel, so 2 things. 1 plenty of fuel getting there, 2 float stuck. The carbs on this are a major pain to remove, they don't seem to fit between the frame and block. Anyway I gave up for the day as I couldn't face it.

Tried again this morning and there was no leak.
Kicked the bike over and she starts but doesn't tick over for more than a few seconds. Can't touch the throttle, just dies straight away.

Idle screw is just touching the mechanism, any more and she won't fire, any less and its not doing anything.

Tried some easy start and it will keep her ticking over, not revving high, just ticking over.

I managed to get a couple of good revs from the throttle but didn't want to do too much.

Just wont tick over, its like it won't rev till its warm but won't run enough to get warm.

Not sure about the mixture screw, don't even know where it is. For those unfamiliar with the Yamaha YDIS carb, its a single carb with extra inlet system, no float bowl on the secondary side, it is fed from the primary. So its not dual carb, more like 1 and a half carbs.

The other issue I have is it is an Italian import (private import) so the engine number doesn't come up on any Yamhaha charts. I am really struggling to find parts like jets etc.

Any advice welcome, I need to use this bike in a few weeks.

TIA

Back to a major carb clean and set. Trying to fix external bits in an ad hoc manner will leave you chasing your tail and drive you crazy - and not fix it.

Go back to the basics - make SURE the carb is RIGHT.
Make SURE the spark is good and strong with a fresh spark plug.
Make SURE there is good compression.
Check the timing!
Then see what happens.

Is it also worth checking the air filter?

Supermotodave, your profile doesn't say where you're from, but here are a couple of sites that may be useful in identifying your TT600 and for buying new parts:

https://www.fowlersparts.co.uk/brows...aha/bike/tt600

https://en.impex-jp.com/catalogs/moto/yamaha/tt600.html

check the air filter, but unlikely to be the cause


that bike shouldnt have a vaccuum pick up point, but who knows, might be drawing air from somwhere, check that there are no suspect un plugged tubes on carb or manifold


did you try to raise the idle screw?

Is the fuel enrich circuit actually flowing fuel when the knob is pulled? Bike will normally run for a few revolutions when cold and no choke. I would unscrew the starter/ choke knob from the carb and ensure all is working correctly.

Is pilot jet really clean? Even when you think they look clean and you can see through it there can be a layer of old fuel varnish that is very hard to remove out of such a small hole. Many an idle issue on my bikes have been solved by tossing the "cleaned" jet with a new pilot jet !

Greetings:
I have a 94 XT 600. Mine sat for about 15 years. Suffered the exact same symptoms. I took the exact same repair steps. And I got the exact same results. The carb is indeed a bitch to remove/replace. So after the first time out I opted to clean the carb in place. Easy & effective.
Buy a can of aerosol carb cleaner.
Disconnect the fuel line from the petcock. Leave the hose connected to the carb. Spray the cleaner into the hose until the hose is full. Crank the engine a bit to suck the cleaner through the carb. This takes a bit of time and cranking. Keep the fuel hose full of cleaner. Let it sit for some time. Over night for example. The purpose is to keep the inside of the carb soaking in the cleaner. I had to do this a few times. And I had to keep adding cleaner to keep the fuel hose full. I guess it evaporates out the hose. I think I actually found a small funnel that fit into the hose. The kind if funnel used for filling old kerosene lanterns. I filled the funnel and laid a bottle cap over it to slow the evaporation process while the carb was soaking. Slowly but surely things improved. I also kept a battery tender connected since this is obviously hard on the battery. A hot battery is a must when these brutes are cold. Also, safety glasses are a must when spraying the cleaner into the hose. Chances are you will get a face full of cleaner at least once. I am a bit slow. I got it two times. Then I found some safety glasses.
This took a bit of patience but it beat the hell out of pulling and replacing the carb multiple times.
After I finally got her running and put some miles on her she now runs great. Still takes a while to start after sitting for more than a few days, but it does always start. Also, my choke is very finicky when cold starting but it always fires immediately once it is warm.
Best of luck to you.
Marty