Second Gen KLR Jetting / Detonation / Oil burning solved (once oil burning starts it probably wont stop, but it might)
So if you've followed my progress on my bike you've seen the first two plug readings, well here they are again
The one on the left is no shims just 2.5 turn out on the screw. the one on the right is with one shim under the needle and 2.5 turns out on screw. Moved in right direction as the scavenge area has some color albeit gray and white. (doesn't show on the pic very well, they're both too white)
So, i decided to add another shim under the needle
so by this image we are still lean but now we've dirtied up the scavenge area
This didnt make sense ... unless. There used to be an issue where the machine could draw fuel from the needle jet at idle or just off idle , which is way too soon. causing a false rich behavior when it was actually VERY LEAN at low throttle openings. Sure as shit the KLR has this issue.
This was an issue back in the late 90's early 2000's on a lot of models.
this is a picture of the needle and slide using a mirror. the at rest position of the slide was too low making the air under the slide move too fast drawing fuel from the needle jet at idle when fuel should not draw from that circuit until much later. This slide if you look to the edges is raised cause i took the photo after the oring was put on.
The solution is easy
A #210 Buna-N o ring stretched over the slide will raise its AT REST
height 3mm or so increasing the available volume and consequently lowering the air speed under the slide at idle and just off idle because that area is the butterfly valve, bypass ports and pilot jets job. (this was a Kawasaki directed procedure for many many models.) I remember doing this mod on a klr 250 years ago and many many atv's the cvk38 and 40ls were bad
I put the o ring on and removed one of the two shims and thats it. And ran the bike (stock #40 pilot), it instantly had a Huge lean condition just off idle, it just bogged confirming my theory.
IT Definately needed #42 Pilot now and 1 3/4 turns out on the fuel screw should be about right. And one shim under the needle. 2 was too much.
what this mod does is isolate the needle effectiveness to a higher engine rpm/throttle opening where it is supposed to be so it can't affect idle and just off idle.
here is my redneck lawmower tank for running it without the fuel tank while i was testing. lol
going to run it a bit and will pull plug and post pic. But this problem is the major cause of all those running issues i've been hearing
the coolant temp spikes
the oil burning
premature rod failure.
I'm not done with the jetting now that the carb circuits are operating where they are supposed to i can jet it pretty easy now it could very well be perfect as follows.
i took it for a short rip and again an marked improvement in power and smoothness off idle and in the mid range so drastic improvement from stock.
Might not need any shims under the needle with the o-ring on the slide and the #42 Pilot 1.75 turns out on the mix screw. This is the part i have to check now that the problem is isolated.
Right now i'm running :
#210 Buna-N o ring on the slide (made for petroleum products)
#42 Pilot Jet
1.75 Turns out on the mix screw
1 0.025" shim under the needle (probably not needed)
145 Main Jet
spark plug gap 0.07mm (0.031")
2009 KLR 650 STOCK except for thermo bypass and doohikey, custom 3/4" lowering link
87 Octane fuel
65 deg ambient temp
This works really good, will verify with plug readings but its damn good. (Remember the little hole on the bottom of the slide goes towards the engine)
27 years as licensed motorcycle Mechanic