problem cant figure it out

[88 250r]

i have a 88 trx 250 r and i just now put a esr 310 head on with 38 mm carb and esr reed with cr ignition i put a 48 pilot and a 185 main jet the bike starts and runs but wont take the rpms when you get more than half throttle it wants to break up really bad it does worse in the lower gears does anyone have any ideas what might be wrong

[2muchquad]

sounds like your jetting is too rich.Try going down a size on your main,your clip position may have to go up one on your needle as well.;)

[88 250r]

how do you move the clip

[methyman]

Before you mess with the jetting try closing up th gap on the plug to .018 first. The bigger bore with the higher compression will try to blow the spark out which will cause the engine misfire. I have been there and done it. I spent all day trying to jet my ESR330 with no luck and came on here and someone told me that little trick. Good luck and enjoy.


Later

Matthew

[2muchquad]

The bigger bore with the higher compression will try to blow the spark out which will cause the engine misfire.


WTF :confused: :rolleyes: :confused: :rolleyes:

[Dave83]

Your main seems a little big.I run a 170 in my 38mm at about 350' elevation.The spark plug gap is a good possibility as Methy metioned.I run mine at about .020.Like he said,the bigger bore w/higher compression can "blow the spark out".

[88 250r]

well i changed the needle to the forth clip and gapped the spark plug like yall suggested but that didnt help the problem so i checked the compression and it only read 90 and i got a high comp head on the 310. the cylinder and head are not leaking to my knowlede and it is a brand new bore with brand new piston and rings so the compression should be way higher and i have rode the bike for about two hours so the rings should be seated but the bike starts on first kick and runs but wont take the rpms just breaks up real bad so suggestions on what wrong would be appreciated and sorry for the long post but i am stumped on whats wrong

[JIMFROMTEXCO]

try another compression tester. let the engine warm, then put the tester on, hold WOT and kick until the needle stops moving on the tester.

is the bike hard to start? how is your plug looking when it comes out? were does it start to break up at?

what are you running for gas and oil?

[Dave83]

Something is up with your compresion tester or you didnt check it correctly.At90 psi,the thing would be almost impossible to start.Like Jim said,warm the engine,then check the compression.Hold the throttle wide open and kick the crap out of it until the needle on your guage stops moving.If you have the high compression dome,you need race fuel.You may be experincing detanation.If you are using race fuel,then Id start jetting down on the main.If I rember right,I started out with a 180 and it acted alot like what you describ,worked my way down to the 170.Its still rich when its really warm out.

[88 250r]

the bike starts on the very first kick and i am running 110 leaded race gas and the plug is a brownish black like it is to rich but i am worry about the compression i held the throttle wide open and kicked it for ever and no change i used the compression tester the other week and it worked fine but the bike breaks up real bad when you try to get hard on the throotle or the top of every gear

[JIMFROMTEXCO]

it sounds like your main is to fat, put it on a diet till it feels right

[88 250r]

so you think the compression test is not reading right

[Dave83]

You have got to have more than 90psi if it starts that easy.I let mine get down to 120 once and I had to almost pull start it.I still say your fat on the main.Some other things to check(from personal experience) are the couterbalance bearing holder behind the stator cover.I had one crack and it would flex,changing the timing when it did it and then put an ohm meter on your coil.Again,I would drop it to 180 main,i bet you will still end need a smaller jet to get it right,but that would let you know you are headed in the right direction.

[2muchquad]

Like he said,the bigger bore w/higher compression can "blow the spark out".

bs:D i think there may be some wrong use of terms possibly.Last time i check a spark jumping a gap is almost instantaneous,its not gonna burn long enough to be blown out by pressure

[Dave83]

You can call bs all you want.The R has a relatively weak spark when everything is perfect.You go adding more compression(pressure) and it can and will prevent the spark from jumping.You are right,the spark is instantaneous,but the piston is already up pushing all that pressure against the plug before it fires.Been there,done that.I had a stock cylinder at 225psi and couldnt get it to run at .026 gap.took it down to .018 on some advice i got at another forum and took care of it.I now run it at .020 with the ESR 310.

[86 Quad R]

the ole "compression fanning out the flame" generally doesnt rear its head on the CR ignition but is possible. i'd suggest that you start with the man jet and work your way to the needle position.

remember the circuits overlap.

[JTRtrx250r]

Originally posted by 2muchquad
bs:D i think there may be some wrong use of terms possibly.Last time i check a spark jumping a gap is almost instantaneous,its not gonna burn long enough to be blown out by pressure No BS man, its truth;)

[86 Quad R]

Originally posted by JTRtrx250r
No BS man, its truth;)

the truth, the whole truth en nuttin but the truth. :cool:

sup jeremy! aint seen you typing around these parts in many a moon.