KLX cam timing

[gtmpaul]

Hi all,
finally got round to doing the top end my KLX, new piston, rings good standard head and cam, valve lap and guide seals, hopfully stop it smoking and fouling plugs.
the bike starts fine but feels flat above 1/2 throttle, I'm a bit reluctant to give it any more revs until it has run a bit longer.
When I timed it up I used my KLX 250A manual, I assumed the A and B models used the same engine.
Now looking through the B model manual shows a different setting for the cam, has anyone come across this before?, is it a revision or mistake.
My bike is a B1 model but I'm sure I've timed it as an A1.
Paul

[pokey]

KL250 didnt change much all thru the range except for one damn thing. the heads and cams. They chose to change it every bloody year. the head must match the cam but will interchange  to different models as a set.
 I dare say the KLX would be the same

[derail]

Hi Paul,
  I have a 1981 KLX250,(B model) the cam timing is set on the KZ200 mark. The KZ (road bike) has advanced cam timing compared to the KL so top end performance is improved. There are no differences in the A and B model piston, head or barrel so setting to the KZ mark should not provide you with any problems.

[gtmpaul]

Hi everyone,
I've now re timed the cam to the KZ200 settings, the difference between the settings when you mark them out on some paper through the sprocket is very slight.

When the engine is started it still is missing above half throttle.

This was the reason I pulled the motor apart was to stop the smoking and lumpy running, which I assumed was caused by the rings blowing by.
Maybe the original problem was elsewhere, I've swapped the coil over but no difference.
one of my theory's is the bike should be running a battery, this had been removed but wiring is just taped up,
I wondered if the voltage would be all over the place with no battery. I've ordered a new battery, plug and cap,
If these don't make any difference I'll start on the carb.
The plug used to be always black, I thought this was just a symptom of the smoking.
All the jets are standard in the carb and it starts from cold normally without choke.
Any advise would be welcome.
Paul

[derail]

Paul,
 

[derail]

Paul, I would doubt that its the battery.
I had some trouble with my KLX  missing from 3/4 to full throttle. In the end i discovered that the air box was the restriction. I put some holes in it and now it works well. My bike is highly modified however so if yours is standard and the spark plug is coming out rich, I would do the following.

 Check that the air filter is in good condition, if not replace it and give it a run. ( I am assuming you have removed the top cover from the air box , if not throw the top cover under the bench)
If this does not fix it , next go down in main jet size to a smaller jet and see if it improves.
 Does the bike have the standard carb on it?

[gtmpaul]

Thanks Derail
I'll try the new pug and cap next, does yours run without a battery?
The lid for the air box was something I'd been looking for for ages, I have recently fitted one.
As I use the bike for trails it often goes through deep water and I've always been concerned about sucking up water, I'll try it with a clean filter and the lid removed.
Another issue is ignition timing, apart from the air gap on the flywheel is there anything else to check?
I'll be doing these in a week or so, we're off for a short break with the kids tomorrow.
Paul

[derail]

Paul,
 I have never run a battery and not had any problem.
 As far as the ignition timimg is concerned,its pretty well fixed, I just set the air gap to 1mm
Regards
 Darrell

[vmx42]

Hi Paul,
The list of things you changed or replaced is fairly extensive but you didn't say if you had the cylinder rebored or honed? Has it stopped smoking?

I would be doing a compression and leak down test to eliminate any problems in that area [eg. a cylinder that is out of round, or leaks around the valve stems].

As for the reason for not revving out and running 'lumpy' as you put it. Does it happen under load or when you just rev the bike when it is on the stand?

To me it sounds like a dud winding in the ignition. That would explain why  the plug is always black. I know it could be jetting but these bikes are in a very low state of tune and if as you say the jetting is standard the bike should still run  well and rev out even if the jetting is not quite optimal.

Have you checked the earth on the coil and CDI?

I will keep pondering it for you.
Good luck
VMX42