1st congrats on getting it back together, condolences on it not running.

not starting after a long sit not uncommon.  most likely caused by dry bowl.  best to put it on prime for a bit to fill it up 1st then back to run before you start.  

Stuck float not uncommon either, dries out sticks to something.  rap on side of carb with plastic screwdriver handle.

OK, now the rest you're abit unclear on.  read thru SW's carb cleaning thread in the tech section to familiarize yourself with proper terms.  

There's a vac hose that connect the carb to the petcock, make sure there's no gas in it, leaking from it, bad, very bad.

There's 2 vent lines, 1 on each side of the carb (symmetricaly) if there's a stuck float gas will pour from these and it's the best.  the alternative is that it flows into the intake and down into the crankcase, bad, very bad.  check your oil level, is it higher?  or it can go into the air box, just drain it if it has.

go for it

if it was a cage, I'd say you got a vacuum leak.

check around make sure everything is tight.

check that vac hose

I know when I've left the choke on the throttle response is slow.
And read somewhere that if you make a hole somewhere it will speed up response.
So maybe you have a clogged port somewhere or a sticky slide.
Can't hurt to clean it.

I just went for a ride to a friend's house and back, ~30 miles. I noticed that I hardly used any throttle at all - a slight touch would have a not-so-slight effect. The racing was the worst in Neutral. I am starting to think it is the throttle cable - seems like there is too much tension on it. When the throttle control is completely off, at the carb there is still some distance between the tab on the throttle and the idle screw. I didn't touch the cable adjustment while I was working on the bike, so I'm not sure if something else might still be the problem. Does the cable itself need to be greased or should I try more slack?

Hi from me again!

When you are diagnosing things try to look at the simplest things that can be checked easily 1st. An awful lot of people get technical and end up with carbs in bits over a stuck throttle or float which could be sorted in a few seconds because they overlook the simple stuff!

If the engine ran fine before then float level setting, jetting etc was ok then so it follows it still should be?

When the throttle is closed is the cable closed off against the idle stop?
Winding the idle stop screw out won't do a thing if the cable has no slack left. So you get a fast tick over and no engine braking. If it isn't adjusting properly then then sort that first, and ensure the cable opens closes the throttle smoothly and there is few mm of slack when throttle is closed.

Really you should only put a petcock to prime for maybe 1 minute max when a carb has been dry or bike doesn't start after not running for a while. The carb will fill up fairly quickly as long as the float isn't stuck, (tap side of carb gently with a bit of wood or similar whilst petcock is in prime of you think float may be sticking, the jolt will usualy help gravity to drop the float needle open). You can check that fuel is in float chamber by loosening the small screw at the bottom and checking fuel flows through it. Then petcock should be put back to normal on position before starting bike, (that way you don't ride of into the sunset with the carb in prime position).

To check petcock and vacuum hose is working properly pull fuel line from the carb with petcock in on position, fuel shouldn't flow out. Give starter a short press to crank engine over and fuel should flow out, and then when engine isn't turning the fuel should stop again. Then Pull Vacuum hose off and check fuel isn't getting down there.

Float needles are designed to maintain correct level when an engine is running but if a petcock is left in prime then the fuel is open straight from the tank to the float, sooner or later the force of gravity and possibly build up of pressure in fuel tank if ambient temperature rises will overpower the float and fuel will pass and end up leaking into the carb inlet and hence the air filter. (The fuel tank filler cap is designed to vent but a positive or negative (vacuum), pressure has to build up first). That is why this type of petcock is fitted to many carburetted bikes as it automatically turns fuel supply on and off by the vacuum hose and prevents the risk off petrol overflowing the carb if you forget to turn fuel off.


If the engine has stopped with the intake valves in the cylinder head open, then some fuel could leak into the engine. If you suspect this may have happened then drain the oil from the engine and check there isn't any in it and that the oil is still nice and viscous. It doesn't take very long to do this and if the oils ok you can put it back in.

As you have had fuel leaking through air filter make sure air filter is sound and is dry.

Have a good look at the rubber inlet pipe etc and jubilee clips to make sure no splits or loose bits where air can get in.

All these checks sound a lot but actually take about 10 to 15 minutes to do.

If you find nothing wrong and you have a good spark at spark plug then it's time to consider more drastic action.

One thing which I think is a good idea is every 3 or 4 months remove the screw at bottom of float chamber and drain it out. That helps stop sediment building up and ensures fresh fuel is present.

One very important thing to be aware off is this.
If a petcock is left open (in prime on a vacuum operated one), when you refuel at a petrol station then the following is likely to happen.

You fill fuel tank with cold petrol from the petrol stations underground tank and put fuel tank filler cap back in, then you go to pay with your fuel.
While you are paying the cold fuel starts to warm up, (from heat of engine etc), and the fuel and the air space in tank expand causing a rise in pressure inside tank. The petrol tank filler vent will prevent this pressure getting too high by venting. But if petcock isn't closed this increase in pressure may overpower the carburettor float and let fuel pass. You now have a situation where the fuel level is too high in the float chamber causing the engine to flood when you try to start it. Worse you could find the carb overflowing when you return and petrol dripping over hot engine and exhaust!

When I reinstalled the carb it grabbed the cable and put extra tension on it. Once I cleared that up it idled quite nicely. However, with the lower RPMs I heard some chattering, and I'm pretty sure it's from the right side crankcase, but I can't be sure yet. When I had it all apart the chain plunger was out 17mm so I figured I would order the parts and replace the chain during the next stretch of bad weather. Looks like maybe I don't have that luxury. In any event, when the engine is cold I'll re-check my valves and re-inspect the chain tensioner.

meck wrote on 06/25/08 at 07:27:05:


Careful - you have an '88 the common white spacer ideas apply to '95 and later carbs - the 86-88 are tuned pretty different from the factory - no where near as lean as the later model carbs that are set to make the EPA happy

on your backfire - I'd keep looking toward the exhaust - head/header gasket at the head and the muffler pipe joint