Need some help with my 86 Kawasaki KMX

[sa_94]

I recently got myself a 1986 KMX 125 of a friend for £150, awesome price even if it has a few issues.

Anyway, at first it would stay running for more that about 20 seconds so I put a new spark plug in and solved that problem.

The issue I have now is that it doesn't rev up properly, in neutral it will rev all the way to 10k but a bit slower than it should.

However when in gear, all gears this is, it has very little power at low rpms and will bog down going up the revs almost feeling like it wants to stall, seems to run better once it gets to higher revs though. It also doesn't like to idle, just dies when the throttle is let off, I can get it to idle with the idle screw in near all the way though that isn't a good solution. The is also quite a bit of oil coming from the exhaust, nothing that I'm too worried about though.

I've taken the carb apart and given it a good clean not that it seemed to need it and it didn't help at all, also checked the reeds and found to my surprise that they were carbon reeds that were also fine.

My guess would be some sort of fuel problem but I'm not sure why it would rev all the way up fairly easy out of gear but not in.

I'm good with mechanics and such so I can do all the work myself but actually figuring out what work needs doing is another problem.

Sorry for the long post and I look forward to your help and advice.

[SW Motech Shop UK]

Some good things to check would be:

Plug cap and ht lead
Mixture setting
cylinder compression

If the carb is clean and set up correctly it will most likely be electrical and a worn out cap and lead would be the first things i would change.
____________________
https://www.motorcycle-road-and-race.co.uk and https://www.sw-motech-shop.co.uk/ and https://www.motorcycle-luggage.co.uk/

[doggone]

What's the air filter like, you could run it to test without one.

[sa_94]

Turns out there was no air filter which I knew.

What I didn't know was that when there is no air filter that the air box can't draw air properly.

It now has full power and is damn quicker then I though it would be, the thing does 60mph in 4th gear.

However I am still having the same idling problems so some help with that would be appreciated.

[GrumpyGuts]

I would check the carbs as mentioned. Check all the jets (clean I mean), float bowl, needle heights and adjust the idle screw.

If that doesn't work or has already been done, check that there are no air leaks around the inlet manifolds. My old bike had this problem and caused the bike to run too lean which somehow also affected the idle, too.

While you're at it, just check the throttle cable is routed properly by turning the engine on and move your handlebars from left to right fully, listening to the engine if the cable is being snagged.
____________________
My Bikes: Lifan Beat 125cc '11 -> Suzuki B120P '76 -> Suzuki EN 125-2A '08 -> Honda CG 125 '04 -> Honda CB600F Hornet '98 -> Kawasaki ZZR 600 '99 -> Kawasaki GPZ 500S '95 (Current)
Theory test passed - 09/02/2012 >>>> Module 1 passed 24/07/2012 >>>> Module 2 passed 24/10/2012

[sa_94]

I've already had the carb apart and cleaned it twice so, everything seems airtight so that shouldn't be a problem, throttle cable is also fine.

When I start the bike up after being sat for a while it'll idle up at around 3k rpm until it starts to get warm then it drops off and dies, it dies a lot quicker if I give it some revs.

It does idle for a little longer with the idle screw near all the way in but it'll still cut out after a while.

[sa_94]

I got an air filter of a kmx 200 which fits fine, I'm still having the same revving and power problems though.

I see no reason that there should be plenty of air getting to the carb but it only works properly with the side of the air box off.

Any ideas why this would be?

[dangerousdave]

Does sound like an issue with the mixture strength/jetting.

Here's the stock setting for the Kmx

Mikuni VM26SS 
Main Jet:102.5 
Pilot Jet: 25 
Needle Jet: O-4 
Jet Needle: 4FL44 
Needle Position: 2nd from top 
Float height 21mm +/- 1

This is a good basis to start from. There may be slight adjustments to be made, especially to compensate for aftermarket reeds and exhaust.

If the exhaust is leaking, or if there are any leaks on the KIPS chamber gasket (common), or any air leaks between the cylinder and airbox, these will mess up your jetting.
____________________
1988 Kawasaki KMX 200

Previous: Yamaha YZF1000, ZZR600, KMX200, DT50, KX80, CG125, PF50