1999 KDX 220 Sputtering at high end

Got questions? We got answers....
Post Reply
Kenrevho
Member
Posts: 4
Joined: 04:28 pm Jul 03 2009
Country:
Location: Vermont

1999 KDX 220 Sputtering at high end

Post by Kenrevho »

Previos own was running a desert pipe and it was popping at high end last year. Bike has since been rebuilt with new top end. FMF gold series GNARLY head pipe with an FMF tip. I am getting hesitation up high in every gear. Sounds like it is starving for something,but not sure what.
I've gone from a 145 and a 150 main jet with and without air box cover on the bike. The air box cover does have holes in it. The jet neddle is on center clipI have gone from 1 1/4 to 1 3/4 on air screw and now I'm back to 1 1/2 out. Then I went to a 158 main jet then to 160 main and no change. Had coil check by local shop and was told it was OK.
Any ideas on what to do next? Could the coil be bad even though it checked out OK. Any imput would be great!
Thanks,
Ken
User avatar
Colorado Mike
Gold Member
Gold Member
Posts: 1921
Joined: 11:42 am Feb 25 2005
Country:
Location: Colorado

Post by Colorado Mike »

check the timing? KIPS operation? Air filter clean and properly oiled? new properly gapped sparky plug? reed valves in good shape? If no air leak from bad crank seals or gaskets, could be the coil or the CDI. It would be good if you had access to another bike to swap those and test. oh, also make sure your kill switch isn't coming on from high rpm vibration, but that's a longshot.

Also, when you say new top end, you didn't put the stock piston in there I hope. They're grenades you know.
Mike

Life's tough, it's even tougher if you're stupid.
'04 KDX220
Kenrevho
Member
Posts: 4
Joined: 04:28 pm Jul 03 2009
Country:
Location: Vermont

Post by Kenrevho »

The bike has a wiseco piston and boyesen reeds. When piston blew previous owner pulled out broken piston by the bottom of the connecting rod. Is their a quick and easy way to check for an air leak in the crank seals or gaskets? I do have access to another bike so I will swich out the coil and CDI to see if that is the issue. Thanks alot for your advise.
Ken
User avatar
Colorado Mike
Gold Member
Gold Member
Posts: 1921
Joined: 11:42 am Feb 25 2005
Country:
Location: Colorado

Post by Colorado Mike »

Good on the Wiseco. Checking for an air leak is quick and easy but only if you have a rig to do it. Unfortunatley a store-bought one is expensive. Motion Pro has one for over $200. I made one for less than $20 with parts you can get from a home center. You need a low pressure gauge and some NPT fittings to create a way to block the exgaust port and pressurize the intake port. You pump it up to about 6-10 psi, and then measure how much it leaks down over a few minutes. I woiuld think some web searches might yield some examples.
Mike

Life's tough, it's even tougher if you're stupid.
'04 KDX220
jbowens2401
Member
Posts: 301
Joined: 08:26 pm Aug 18 2009
Country:

Post by jbowens2401 »

could your main jet be too large...you may be getting too much fuel. If you are running the stock 33mm carb, that would be my guess but I don't know your elevation and temp range. Good luck...let me know if it's the jetting b/c I'm trying to get mine dialed in as well.
User avatar
kawagumby
Gold Member
Gold Member
Posts: 927
Joined: 10:09 am Nov 30 2006
Country:
Location: California

Post by kawagumby »

I second the mainjet check first. You can see what I run in my 220 in the bike profile below. The jetting noted works well all the way up to about 4000 feet....
1994 KDX200, Beta 200rr, yz125, yz250, kx100 modded for adult, gasgas contact 250.
User avatar
canyncarvr
Gold Member
Gold Member
Posts: 6943
Joined: 01:07 pm Nov 05 2004
Country: US
Location: The Mythical State of Jefferson

Post by canyncarvr »

Up to a 160? :shock: On a 33mm carb?

Re: 'I second the mainjet check first.'


Uh...yeah!


1. ..am getting hesitation up high in every gear.

2. Sounds like it is starving.

3. Sputtering at high end.

Those three descriptive phrases relate to different things.

The first two I could understand to be normal for a 220. One of their 'virtues' is poor breathing in the upper RPM ranges.

It is not a 12-14KRPM bike......

Consider the source
Using a perceived level of knowledge to boost my self worth.
Non impediti ratione cogitationis

bike profile: !clicky!
Post Reply