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88 CR500 jetting

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I'm having some issues getting my 88 cr500 dialed in. here are the specs and the story behind it:

elevation: 400-500ft

humidity: 50-85%

current temps: 40ish degrees F

88 cr500

-39.5mm PWK keihin carb

-milled head

-1mm (i think) overbore

everything else stock as far as i know (new bike)

The bike was extremely hard to crank. I finally got it cranked up with the choke on and it wouldnt idle and as soon as i turned the choke off, it would die. At the time the bike had a 175 main and a 55 pilot with the needle clip on the 3rd (middle) position.

I gathered that it was running lean since it wouldnt run with the choke off. I changed the main from a 175 to a 178 and the pilot from a 55 to a 58 and lowered the clip all the way to the bottom position.

It still is hard to crank and it doesnt run well with the choke off.

Given the cold weather, milled head and PWK carb, how much richer can I expect to jet it?

Im not sure what needle is currently on it, I just bought the carb off of ebay and it has whatever the default needle is that comes in it.

Thanks

Edited by Matt Defore

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The main jet will not effect idle, leave it alone for now.

Make sure that your air screw is set to the factory amount of turns, I think it's one and three quarter turns out from all the way in.

Check the intake boot and make sure that it is sealed properly, along with the reeds and reed spacer. Use RTV if the rubber seal that is built into these looks rough, just a very thin amount.

Tighten the bolts in a criss cross pattern.

How many turns in is the idle screw?

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Check you cr500riders.com and do a search.. I got all my info form there when I had my '89 and mine ran MINT after I installed a new exhaust and did some engine work

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The main jet will not effect idle, leave it alone for now.

Make sure that your air screw is set to the factory amount of turns, I think it's one and three quarter turns out from all the way in.

Check the intake boot and make sure that it is sealed properly, along with the reeds and reed spacer. Use RTV if the rubber seal that is built into these looks rough, just a very thin amount.

Tighten the bolts in a criss cross pattern.

How many turns in is the idle screw?

where can i read more about the reeds? Should the reeds be touching to make a seal when you pull it off the motor? i looked at them and there is a slight gap, maybe 0.5mm or so.

ill let you know about the idle screw when i get back near my bike

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EDIT

PS - it's actually a 39.5mm PWK carb if that makes any difference, not a 38mm. i was wrong about that

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ok, i looked at the idle screw and the air screw

it cranked up easily today because it was about 18 degrees warmer than yesterday, a cool 60 degrees.

the idle screw is 1.75 turns out from all the way in, and it idles normal at that point, seems like it is in pretty far.

to make matters more confusing for me as a first time jetter, i couldnt find much of a difference in the idle quality as i adjusted the air screw. am i looking for a significant difference in the RPM's or is it subtle?

i was only able to ride around the parking lot a little today gears 1-3 at about half throttle or lower and i pulled the plug and it was kind of wet and oily.

thanks

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I can't remember what the stock setting is for how many turns out for the idle screw..

Besides the point, you need to do a 1/4 throttle run and get a plug reading. This will tell us if your pilot jet is rich or lean.

If you can get the bike to idle, then leave the air screw alone for now. Mark your throttle in 1/4 turn increments. with the bike off use white out or something or smalls strands of masking tape for the markers. Put a marker on the throttle tube (your grip) and one on the throttle tube housing to mark 0 throttle. Turn the throttle all the way to full and mark the throttle tube again. Find the half way point and mark that, and then finally find the 1/4 point and mark that.

Warm the bike up, and take it to the parking lot and ride it ONLY at 1/4 throttle for a little stretch. It's best to do this through ALL the gears up to 5th, when the bike maxes out on speed at 1/4 throttle pull in the clutch and hold the kill switch until the bike dies, roll to a stop and pull the plug.

You're probably going to need an area that is bigger than a parking lot btw.

Post a picture of your plug, get a detailed one. If you don't know how to do a detailed photo with your camera, there is a "macro" setting that when used, you hold the lens about an inch away from the target and shoot your photo. The image will come out crystal clear and we will be able to tell you if you are rich lean, etc.

There's of course more to the testing, but we have to start somewhere. Things may seem overwhelming but I'll try and help you as best I can if you stick with it.

IT's either this or your bring it in and start paying 80-120$ an hour for someone to look at it.

However, if they have access to a dyno, then your going to have a bike that is tuned to pretty much perfection :moon:

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