too rich?

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Well-Known Member
Delta B.C.
hi guys i was runnin the baja today and it was a little sluggish in the midrange the rpm didnt change much till it was hammered and when i come to a stop it take about 10-15 seconds for the motor to slow down it stalled and i,m haveing a hard time starting it..i geuss i should check the plug..what will i be looking for..thanx
sounds like you have the carb a little rich pull the plug if it is very dark in color it's junk if it's a tan ashey color and the porcelion is not cracked than you have other promblems but im sure the plugs fouled put a new one in run it to temp if it's still seems slugish lean it out 1/16 of a turn and test it again.
how tan? light tan? if it is a pretty light tan,

take the muffler off, look at the piston as it passes by the exhaust port. look to the right side of the exhaust port and just under the piston ring. can you see any damage there? if you do, then its time to take the cylinder off and look at it at the exhaust port, clutch side bottom. if the piston was damaged then the cylinder probably has damage in the same spot, just under the right side of the exhaust port. if you have damage there also, then the motor was lean siezed.
ie ran to lean on the needle settings and it overheated, which melted the cylinder plating at that spot, which is the spot on these motors that sees/gets the least amount of cooling, but no amount of cooling will save an engine from a lean sieze. it a fuel flow ( or lack of it ) issue.

but the fact you say it reved high for a few minutes and then stalled make me think you have an airleak. most likely the cylinder gasket...

time to trouble shoot deeper.
inspect the cylinder base, look for the gasket to be sticking out anywhere, or big wetspots by the cylinder gasket is a sign of a leak.
hope is something simple, but trail and error troubleshooting is whats needed now to figure out what your problem/s is/are.

Thanx for the info greatly appreciated, the base of the cylinder looks like there could be a bit of a leak and the pipe needs a better gasket i,ll have to dig in tommorow thanx again
Well there is no damage to the piston but the base gasket does stick out and it looks like theres a little seepage so i guess thats my next step i also need to clean out the pull starter..only the last 8 inches engages
prolly blew the head gasket, or the cylinder bolts loosened up a bit and that let the gasket get broke and pushed out.

replace the cylinder gasket with a .020 cylinder gasket from Zenoah or CY ( the zen is a tad better gasket) or use the .020 copper cylinder gasket and use a good hi temp sealer on it like Ultra Copper from Permatex.
if your motor isnt the stock motor, post up. some motors use different gaskets.
I bought it second hand i know its a c.y. and its had a big bore, and a reed kit, i,m not sure what displacement i geuss i should measure the piston dia. ? i don't think it has a stroker crank i definatly need a better air cleaner..found a fine layer of silt in the carb..not good do any of the sellers on this board sell the gaskets
the side of the cylinder should have some markings on it which will say what cylinder bore is and the stroke, ie the stock 23 says 28 32, ie 28mm stroke and a 32mm bore.

considering it has a reed, there are some other things to check out. does the reed cage have a hose on it going to the carb?
its possilbe the reed is bad. If the reed cage is the oneils bros, i have heard of some bad reed pedals. you may just need to put a new reed pedal in.

you can get new gasket form most any of the forum sponsors on the right.

if you have the numbers 28 36, then its a GP290 topend. (Big Bore option) and if so, this motor in stock form has more Compression than the others. at about 18:1. i blew 3 cylinder gaskets on my Race Ported 28.5 topend, and finally used the copper one.

grab a pic maybe, and get this bit of info and post it up, cant be too much. but finding the exact culprit can occasionally be a PITA>
Thanx alot, the # looks like its under the ps shroud i,ll dig into it tommorow and let ya know what i find..the fram filter was lettin in alot of crap so bad reed could be it
pulled the pull starter off and noticed its very easy to turn the motor over no compresion i can hear it leak out the exhaust port
Thats the one..well i cooked the motor big gouge in the cylinder it was a 28-35 and i don't think its a reed cylinder either ,looks like mud in the bottom end i,ll get some pics and we can post as WHY YOU NEED A GOOD FILTER-PRE FILTER. DDM has a 3.75 hp billet head 29 motor for 200 and 7 shipping good deal so i,ll be ordering that tommorow. What kind of difference does a reed make is the extra cost worth it
the new top end should be ported to work better with the reed cage.

just dropping the reed cage on will get you some gains. but haveing the cylinder ported for the reed cage will get you alot more performance.

fwiw, Hostile Hobby has pre ported topends for these motors from OBros.
so 28 35. that says your stroke is 28mm and the cylinder is a 35mm bore.

ie the CY29RC motor.
imhonesto, stay away from the headkit motors. the heads tend to warp once overheated, and will stay warped, typically causing a leak at the cylinder head.

what do you want Torque Or Top RPM.
If Torque, start out with the GP290 topend (28 36), its a better cylinder than the cy29rcs, and will wear better. plus no HeadKit to cause issues down the road. sure its not as cool looking as the headkit motors, but which do you want, cool or useable. lol

if you want RPM, then grab the Zen G260RC topend. it will rev up higher due to the smaller piston/weight. ect.

well that sucks, I just got mine ready to run and yours is cooked. get 'er fixed up then. I have a digital steering servo and 2 non digitals on throttle/brakes. I had my radio set for fast frame rate for the steering but the throttle servos glitched. I changed to normal frame rate and was running outside my detail shop last night and had zero problems. amazing how loud a jetpro pipe is at 11pm in the middle of a cemented industrial complex LOL
Thanx for the info it changes my plan a bit i,m gonna see if i can find the gasket set from Wes to get it running as for the motors bottom i don't think it will last so i,ll pick up a good non headkit mtr complete as opposed to just the jug and piston , thanx Timmahh for the info
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