erratic idle sometimes

[DNA]

Hi,
I am trying to help my 10 yr old nephew out with his blaster. It's a 2000, I tried to use the troubleshooting guide but it didn't help. I know very little about quads But I did do a little reading first, can't figure out the problem. Here is what it is doing, starts first or second kick usually but has a erratic idle this only happens after it is ridden for a while. I tried what my uncle said about spraying brake cleaner to see if it has a leak, around carb and cylinder, that didn't do anything but remove some dirt and paint. The quad is all stock with a fmf pipe we did pull the carb and look it has a 270 main and a 32.5 pilot my uncle says. It's clean as he took all the little brass things he called jets out sprayed them and then used the air compressor to blow it all out all over me! He says it's overheating and detonating but I have no idea. I asked him to explain that and his answer was- means that the motor isn't getting enough air to cool it and causing the gas inside to explode before the spark plug sparks. What? never heard that before but said ok. When I did a google search it took me to here and a few other places, but I figured Blasterforum should know about blasters more than anywhere. He says two strokes should be tested for compression a lot , so we did that and came up with 123 after like 15 kicks, we did it three times with same results. Any pointers on what to look for would be great. I can use basic tools, volt meters. But I'm no mechanic! We won't be working on it till after the holiday as we travel to relatives the next few days.
Thanks in advance have a nice x-mas,
Dan

 

[Awk08]

sounds like an airleak to me .....................

http://www.blasterforum.com/do-yourself-20/build-use-leakdown-tester-10663/

check these too...........

http://www.blasterforum.com/carburetor-138/float-heights-how-adjust-them-50565/

http://www.blasterforum.com/carburetor-138/adjusting-your-airscrew-pilot-jet-51060/


btw....tell unky that the fuel cools the engine not more air

 

[DNA]

Thanks! I am going over to his house tomorrow we will check those few things.

I will see if my uncle has a tester if not I will attempt to make one. I do see that is one of the things that a lot of guys say to do. Do you know what size I will need to put in the exhaust and I do have to take the pipe off or could I plug the end of it. I looked in the manual and see there is a gasket, if the pipe is FMF will is still use a gasket? It doesn't look like there is one there. A big spring thingy that is connected from the pipe to the part that is bolted to the motor. It's a little rusty but doesn't look like anything leaking.

The gas cools the engine? I would of never thought that. I will test uncle Frank! My uncle had the top end rebuilt three years ago, when he first got it and never had a problem with it until now. It's fun to ride.

 

[harley1-5]

don't trust looks a leak can cost you a piston or more

 

[Awk08]

get a 1-1/8" expansion plug from any good auto store, yes pull the pipe and use the plug right in the exhaust port of the cylinder to block it off for leakdown testing.
in that port is where you'll find (?) the round "crush gasket" that seals the stock pipe, or aftermarket flange to the cylinder.
you will want to get a new one, they are 1 time use, IMO...........

Vito's Yamaha Blaster YFS 200 Exhaust to Cylinder Gasket 1988 2006 | eBay

surely they can be found for cheaper than that /\ ?

 

[DNA]

I just looked at the plug chop thread, Thinking maybe after we figure out the idle thing can't hurt to check what a plug looks like so if I read right, you need to cut the threads off the plug carefully and there is suppose to be a ring?? dark brown is good, black is too much, no ring is not enough. is that right?

 

[harley1-5]

yep ring should be tan in color plug chop is essential without proper jetting you could have issues

 

[Blaaster]

Before you make the plug chop run it is important that the float level is correct, the idle is set correctly and there are no air leaks in the system, otherwise the smoke ring may lie about the AFR.

WHEN ALL OF THE ABOVE ARE CORRECT PROCEED WITH THE FOLLOWING.

Warm up motor to operating temp.

Fit new B8ES plug, ride WOT through the gears and hold WOT in 5th or 6th gear for 10 seconds, or as long as you can safely.

Switch off the motor and pull in the clutch, apply brakes to come to a stop quickly.

Take the plug out and replace the old one for the ride home.

Carefully cut the threaded end off the plug to expose the insulator.

There should be a smoke ring of a cardboard or biscuit colour around the insulator.

If it is non existant or a very light colour, you are lean and require a larger main jet.

If it is a lot darker you are rich and may go down a size in main.

I prefer to run a little on the darker side, I may loose a little power but it is worth it for the peace of mind that I won't need a rebuild so soon.

http://www.blasterforum.com/do-yourself-20/how-plug-chop-38674/

http://www.blasterforum.com/engine-13/plug-chop-how-vid-48226/

This is a good to go plug.

This one is a little rich, but I would run it, I like to be on the safe side.

You have to get up a reasonable speed so that you can get the motor to pull strongly.

Then hold it Wide Open Throttle (WOT) for 10 secs or as long as you can.

The idea is not to get speed but to make it pull strong at full throttle to get onto the main jet circuit.

I find I can safely do it on a short run by applying the brakes some.

If you have not enough room you can use 4th or 5th gear with good results.

 

[tbrooks]

if the pipe is FMF will is still use a gasket?

Sounds like you may have already been running it lean if it is an aftermarket pipe. You n uncle need to try and determine if there are any other mods to determine where to start with the jetting. mods+stock jet=lean=bad. Post what you find on here and you'll get an idea what jets to start with

 

[DNA]

Today we tore the carb apart again, float is good at 21mm. Took all the jets back out and cleaned again, when we took the carb apart we noticed there was no gasket material on the carb cap, my Uncle made one out of some gasket material he had it was some rubbery stuff he said could be used with gas and oil. We borrowed a leak tester from my Uncle's friend (after we argued about doing this), hooked it all up and found a tiny leak on the intake where the carbs connects to. We lost 2psi over a fifteen minute period. found a loose bolt was the culprit. tightened it all up and no loss of air. Put it all back together put the air screw at one and a half turns out, but it seems to idle best at little past one and a half, so we left it there. We let my nephew ride it till it for a hour, the erratic idle situation is gone! Then we realized we never bought a new plug, so tomorrow we will have a new plug and a spare. We did pull the plug and it was dark, my Uncle said it is good no need to do that chopping thing, but I think I can handle doing that with out him. Once the quad cooled, I removed the old plug which my nephew says was replaced in March. I proceeded to try to chop it just to see, I ended up cutting the white part however, I was able to get it out of the piece I cut off and hold it on the plug, buy what I read, we are running a big rich. Is that right? As per my first post we are running a 270 main. The only other mod is aftermarket reeds called boysen? That is what the empty pack says Boysen power reeds.

Thanks for all the advice.

 

[Awk08]

no sense reading a plug that has been ran on all circuts of the carb.
it is showing color from all 3 jetting circuts...pilot/needle/main and with the choke on for starting (rich).
a plug chop is done to confirm the jetting of an individual jetting circut.
usually the main jet @ full throttle, but can be done @ 1/2 throttle to check the needle clip setting.

re-read the plug chop guide posted above
warm up bike full, get to where you're doing the plug chop on the old plug, install new plug, do 1 and only 1 wide open 4-5-6 gear run as far as you can, hit kill switch while wide open and brake to a stop, pull that plug and install another plug for the ride back. chop threads off and read "smoke ring" color of that 1 WOT run plug.
do not ride the bike for any length at anything but WIDE OPEN, for checking the main jet.