84 250R running rich

[barnett468]

ok tired everything suggested seems to be better but sputters through 1st and 2nd then seems to clear up and run. once I ride for about 5 minutes it runs good through all gears. it seems like once warmed up good it runs fine. but it still smells rich to me out of exhaust after I ride it hard then let it idle. I have bought 2 smaller main jets but does it seem like I might need to change the slow jet the main is a 150 and the slow is a 50.
thanks for all your help

ok, exactly what was it you tried?

no, 20:1 will not hurt the engine as mentioned . . they used that ratio for a safety margin that is definitely unnecessary with the oils available today . . use 32:1.

the slow jet is not causing your problem because your problem is above where the slow jet has much affect.

reduce the main jet size as i suggested and report results but clean the plug or install a new one.
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[jerkin]

Couple things I haven't seen mentioned. First, clean your air filter, you can't jet properly without a clean air filter. Next do a leakdown test, you will never get the jetting right if your sucking air from somewhere. I haven't been here long enough to know for certain but I'm sure there are pictures of a leakdown tester here somewhere. Basically you pull your exhaust and plug it at the cylinder (rubber stopper with the screw to tighten it works well) then pull your carb and plug in your tester to pump the cylinder up with air, should hold 6 psi for a few minutes, if not you start spraying soapy water around looking for leaks (reed gasket, base gasket, head gasket, etc. can also be crank seals)

A tester is easy to make, mine is just a piece of pvc that fits in the intake and is capped at the other end. I put a tire valve in it to induce pressure and a low pressure gauge (15psi max) to monitor the pressure. Pump it up with a hand pump and watch the gauge. Once you have these things done you can buy a few new plugs and properly jet your carburetor. 20:1 was for the crap oil they had in the 80's, run something decent like Maxima at 32:1 and you'll be more than safe.

Jetting is all done by throttle position, idle to maybe 1/4 throttle is the pilot jet, 1/4-3/4 is the needle and 3/4 to wide open is the main (this is just close, there is some overlap). Pilot is easy, if it idles and the plug is wet when you shut it off your close. Getting close on the needle is easy also, throw it in 3rd gear and hold the throttle half way open, when it winds out as far as it will go stab the throttle, if you gain rpms it's close, if it was already wound tight you are lean, raise the needle one spot and try again. Main is a little tougher and you need some room. Install a new plug and run it down the road wide open for a minute or so, pull in the clutch and shut off the engine. When you come to a stop pull the plug and read it.

[hdd]

went down a size on the jet and new reeds runs like a champ. thanks for all the help. im currently rebuilding another engine for the 250r and confused on the bore size the piston say 50 on the top of it but when I check it with my calipers the bore says 70.21mm and piston 70.15 on the Wiseco site its says 70.50 for 50 over. any suggestions why the difference.

[barnett468]

went down a size on the jet and new reeds runs like a champ. thanks for all the help. im currently rebuilding another engine for the 250r and confused on the bore size the piston say 50 on the top of it but when I check it with my calipers the bore says 70.21mm and piston 70.15 on the Wiseco site its says 70.50 for 50 over. any suggestions why the difference.

xlnt.

ok, where are you measuring it . . you should measure it around 3/8" up from the bottom.

if your calipers are accurate, your piston is severely worn.

you can take a sheet of paper and fold it over 4 times so it is around 3/4" wide and 2" long, then stick 1" of it into the bottom of the barrel then try to install the piston and gently push it past the paper . . if it goes past the paper, the wear on the piston and/or bore is excessive.

if you can push a piston past a piece of paper that is only folded over once, it is a little loose.
.

[hdd]

ok I have 2 84 250R's now one runs great after I changed from a 140 main jet to a 130 both has some sputter until I make a couple of runs then run great. the other one sputters a little more then once I run a little the sputter goes away. On the one running poor until it gets warmed up I am running a 128main jet, good compression I think its something with the carb. I have rebuilt the carb., new reeds, new plug and it looks good light brown but for it to idle I have to turn the idle screw all the way in.
http://youtu.be/nT6UjYVl4ZM (Running good)
http://youtu.be/iemLVS93Bsc (Running poor until it gets warmed up) towards the end you can see it running pretty good.