Need Carb Help

[R3Concepts]

I recently bought a 250R to build a drag bike out of and I decided to slap it back together for my little cousins to ride at the dunes over New Years and can not seem to get it jetted to save my life.

Its a '88:

FMF Pipe
No Lid
Uni Filter
New 66.50 Wiseco
Casting cleaned up, stock port timing
B8ES Plug
40.5 PWK
VForce 3s

Now, the carb I KNOW is wayyyy to big, but I want to see if I can get it to at least run where they can ride it.

Jetting: 45 pilot, 2 turns out, DGH 4th clip, 170 main.

Starts first kick, sounds decent reving in nuetral, get it on the dyno, with any kind of load, falls flat on its face. Wont clean out or "come up on the pipe".

Wrong plug? Reeds were just changed. Pump gas with 927 at 32:1. Wil do a compression check tomorrow, but I dont think thats the issue.

Anything to look into from here?

[jon370r]

1st thing you want to do is close the plug gap to .018 and go from there. 250R's have weak spark and if the engine has had any work done to it (more compression) it will blow out the spark.

[R3Concepts]

Originally posted by jon370r
1st thing you want to do is close the plug gap to .018 and go from there. 250R's have weak spark and if the engine has had any work done to it (more compression) it will blow out the spark.

Ive already done that.:ermm:

[8686]

You say the engine is set up for pump gas, right? If so, I think you're too rich. Put the clip in the middle groove on the needle and drop the main. Drop the main one size at a time (if you have the jets), but you'll prob ably end up around a 160 or so. At least, that's my slightly educated guess.

How does the plug look? Don't forget to use a new plug gapped at 0.018-0.020 each time you change the jetting.

[R3Concepts]

Originally posted by 8686
You say the engine is set up for pump gas, right? If so, I think you're too rich. Put the clip in the middle groove on the needle and drop the main. Drop the main one size at a time (if you have the jets), but you'll prob ably end up around a 160 or so. At least, that's my slightly educated guess.

How does the plug look? Don't forget to use a new plug gapped at 0.018-0.020 each time you change the jetting.

140 psi on the compression check today.

Gone from top to bottom on the DGH, from 40-52 on pilots, and from 145-185 on mains and nothing seems to help.

[R3Concepts]

Quick edit: The motor was put back together with a fiber head gasket, how much compression will I gain by going back to a stocker?

Id like to stay 180psi range to run it on pump gas.

I think that 140psi should be more then enough for it to at least run, and clean out.

Might start looking towards CDIs etc?

[86 Quad R]

just a couple things ta check....have you done a leak down test on it to be sure its goed en sealed? i've seen em leak at the crank case gasket/seal en act as you describe. also, hows the needle orfic?

[R3Concepts]

Originally posted by 86 Quad R
just a couple things ta check....have you done a leak down test on it to be sure its goed en sealed? i've seen em leak at the crank case gasket/seal en act as you describe. also, hows the needle orfic?

Have not done a pressure test. I just slapped a new top end on it so they could ride it. Its eventually going to be a big ESR motor, so Im not wanting to tear it down for this trip.

Everything in the carb is clean and working correctly that I can see.

[jon370r]

I've seen many strange things done to engines that I've taken apart to rebuild over the years. Just check and make sure the pistion is facing the right direction. There was a 250R that went on a trip to Glamis Dunes and the guy was screwing with it all week trying to make it run right. He had borrowed it from his brother inlaw. I bought the quad 2 years later fron the owner and when I changed the dome in the cool head I found that the pistion was in backward. The intake window was on the exhaust side. Explained why it ran like crap all week.

[R3Concepts]

Originally posted by jon370r
I've seen many strange things done to engines that I've taken apart to rebuild over the years. Just check and make sure the pistion is facing the right direction. There was a 250R that went on a trip to Glamis Dunes and the guy was screwing with it all week trying to make it run right. He had borrowed it from his brother inlaw. I bought the quad 2 years later fron the owner and when I changed the dome in the cool head I found that the pistion was in backward. The intake window was on the exhaust side. Explained why it ran like crap all week.

I hear ya on it being something stupid, but the piston is in the right way for sure.

[R3Concepts]

Squish is at .040. Pickup set at .018, plug at .018.

Ran better with a 52 pilot, DGH all the way out of the hole with a small washer under it, and a 155 main jet. Still falls on its face with any type of load.

The slide is a #6...Will going to a 4.5ish help?

Where are all the 250R experts when ya need em??

[jon370r]

7 is the typical slide that gets run in a 250R with a PWK carb.

[R3Concepts]

Originally posted by jon370r
7 is the typical slide that gets run in a 250R with a PWK carb.

I just found where the PWK comes from Sudco with the 6 so thats not my problem...Hmmmm. Getting frustrated.

[8686]

At this point since you've been up and down the jetting ladder I'm going to say it's not a jetting issue. If you have another carb handy I would give that a shot. Are you running a stock ignition? If the ignition is weak you could be chasing jetting problems for the rest of your life and never get it to run right.

[R3Concepts]

Originally posted by 8686
At this point since you've been up and down the jetting ladder I'm going to say it's not a jetting issue. If you have another carb handy I would give that a shot. Are you running a stock ignition? If the ignition is weak you could be chasing jetting problems for the rest of your life and never get it to run right.

Stock ignition with an Advantage Performance CDI. I talked to another guy today that had the same CDI on an '88 and he said he switched it out for a Dyna CDI and the problem went away.

Like you said, I think Im passed the idea of a jetting problem.

[86 Quad R]

you have a stock cdi to try on it?