Go Back   ADVrider > Bikes > Thumpers
User Name
Register Inmates Photos Site Rules Search Today's Posts Mark Forums Read

Thread Tools Search this Thread Display Modes
Old 07-27-2014, 09:52 PM   #1
MidlifeRiding OP
Joined: May 2014
Oddometer: 12
KLR650A Carb Adjustment Question

Hey folks. Just rebuilt an 05 KLR from the frame up. Carb rebuild was part of the work with a Moose Racing rebuild kit.

Factory spec said to set the pilot jet at 1 and 3/8 turns out from lean (all the way in). When I set that, I could not keep the engine from flooding. I ended up setting it all the way back to lean and gradually backed it out until the engine ran fine without the smell/heat associated with running lean and also so that it wouldn't flood. This is roughly 3/4 of a turn out on the jet screw.

It runs AWESOME after it warms up but is still a little too finicky on cold starts. I've re-adjusted the pilot jet both in and out as well as the idle screw. It seems that I can't get it dialed in just right. If I make it run awesome on cold starts then it doesn't run as well as it should after it warms up. If I adjust it so that it runs awesome after warming up, then it doesn't like cold starts. It's one or the other, but I can't seem to find that happy medium between the two.

My question is - are there any tricks or tips that any of you have to finally get this thing dialed in? Thanks in advance for the input!
Patrick Hayden's U.S.A. trip thread
My trip info, updated regularly - MidlifeRiding
MidlifeRiding is offline   Reply With Quote
Old 07-28-2014, 12:05 AM   #2
Beastly Adventurer
Joined: Oct 2004
Location: Anchorage, formerly Spenard (hub of the universe)
Oddometer: 5,275
something ain't right. the pilot system should not be that touchy. check to see that the needle & seat will stop the fuel flow when the bowl is full. you need to apply a vacuum source to the petcock & watch for overflow (engine off). another cause could be float level too high. I forget the spec but (usually) the bowl is full when fuel is just below the parting surface. another possibility is the enricher is out of rig & leaking extra fuel.

if you have a manual petcock, the vac line needs to be blocked off or extra air gets past the carb. there is a brass tube on the left side of the carb for that line & it goes to the pet. if you still have the stock setup, check that vac hose for fuel... there should never be fuel in the vac line. if there is, the diaphragm in the petcock is torn

hope you did the doo
Beezer is offline   Reply With Quote
Old 07-28-2014, 06:05 AM   #3
Joined: Apr 2013
Oddometer: 20
Finicky on cold starts? Are you using choke? There shouldn't be a need for a happy medium. Set it so it runs right warmed up and use choke to start. Warm it up for a minute and all is well with the world.
kyxon is offline   Reply With Quote
Old Today, 01:40 PM   #4
MidlifeRiding OP
Joined: May 2014
Oddometer: 12
Here's the rundown:

I bought this bike non-running and not knowing much about what has been done to it.

The first carb rebuild (issues in original post) was basically done blind not knowing what I had and what mods were done so I ended up reassembling this modified carb (and bike) with a stock jet/needle kit. Had some very "interesting" results.

Second carb clean/rebuild I took the time to learn about all of the mods available and figured out exactly what I had so I could make it my last rebuild (sadly, I still did it a 3rd time :(). I found out that the carb HAD the Dynojet stage 2 kit, 150 main jet and 40 pilot jet (which I swapped out for stock on the first build). Needle set to position 4 from the (flat) end with 1 washer on top.

The diaphram slide was drilled out and after reading the details of that mod I realized that it was drilled WAY too big so I bought another one from Harley and redrilled it to 7/64.

The choke air cut diaphragm was STUCK in the carb and I ended up destroying the rubber boot around it for the 2nd rebuild. Still waiting on a replacement to show up (wait until you read about my insanely awful rig that I'm doing for the time being). This explains my touchy choke where it seemed to be either full blast or none at all which wreaked havoc on my cold start idle.

Found a small crack around the intake boot (post-carb) and patched that one up.

Basically the second rebuild showed me that I was running her very lean with the stock jets/needle on my modified carb/bike (FMF pipes, airbox mod, oem filter (swapped out from a K&N), diaphram drilled, petcock rebuilt, full fuel system overhaul, tank vent mod).

Use the DynoJet kit to richen her up and fix (rig) the choke.

To rig the choke (let the flaming begin because I know this is bad...but it kinda works and allows me to ride the bike in the meantime) I used the plunger metal piece (cut out all of the old rubber seal) and shoved that into the carb where it's supposed to be. Then I used the incorrect flat one (came with the Harley rebuild kit) and put that on top of it to use the fresh seal, then the spring and cap as normal. I know with the added pressure due to the added thickness of the metal plunger from the flat diaphragm makes the system work totally incorrect, and it shows. I basically have the same thing as I had before except now it's more consistent full blast or non-existent because before with the plunger getting "stuck" on occasion, sometimes the choke would work right and sometimes it wouldn't and it drove me nuts!

Anyways, cleaned and rebuilt the carb with the stage 2 kit and proper parts with the best initial settings I could possibly muster and settled on position 4 from the (flat) end with 1 washer on top. It seemed like it should be in range and was what it was initially set at when I pulled it all apart for the first time. Pilot jet of 40.

Seemed too rich.


I cleaned the carb again (why not, just to be sure) and adjusted the needle to the 3rd position with 2 washers on top. Seems to be idling MUCH better and for now, on cold starts I just quickly give it choke (full blast) to get her firing and then back it off and hold the throttle until she'll idle on her own.

I've richened up the system as a whole to try to compensate for the non-functioning choke fuel supply and it's doing OK. Still a few more minor things to tweak but I can't really dial it all in until I put the proper air cut diaphragm in which won't be until early next week. I may back down to a 38 pilot jet if needed when the choke gets fixed but we'll see.

On a side note, there is a chance that I may be doing a baseline dyno tuning on this thing early next week. I'm curious to see how she does!
Patrick Hayden's U.S.A. trip thread
My trip info, updated regularly - MidlifeRiding

MidlifeRiding screwed with this post Today at 01:48 PM
MidlifeRiding is offline   Reply With Quote
Old Today, 02:08 PM   #5
Beastly Adventurer
Joined: Oct 2004
Location: Anchorage, formerly Spenard (hub of the universe)
Oddometer: 5,275
I have fixed over-drilled slides with epoxy... then I usually drill them back to stock..ymmv.

as for jetting.... kehin, dyno, and mic all have different sizes for the same jet number. heres a comparison, can't guarantee the flow rate for same hole size because they are different lengths & have different approach & exit tapers

Carb Jets
Width------Kehein # -- DynoJets # -- Mikuni #
0,0350---- 92,5--------- 92----------- 86,3
0,0360---- 95----------- 94----------- 88,1
0,0370---- 97,5--------- 96----------- 90,0
0,0380---- 100---------- 98----------- 91,9
0,0390---- 102,5------- 100---------- 93,8
0,0400---- 105--------- 102---------- 95,6
0,0410---- 107,5------- 104---------- 97,5
0,0420---- 110--------- 106---------- 99,4
0,0430---- 112,5------- 108--------- 101,3
0,0440---- 115--------- 110--------- 103,1
0,0450---- 117,5------- 112--------- 105,0
0,0460---- 120--------- 114--------- 106,9
0,0470---- 122,5------- 116--------- 108,8
0,0480---- 125--------- 118--------- 110,6
0,0490---- 127,5------- 120--------- 112,5
0,0500---- 130--------- 122--------- 114,4
0,0510---- 132,5------- 124--------- 116,3
0,0520---- 135--------- 126--------- 118,1
0,0530---- 137,5------- 128--------- 120,0
0,0540---- 140--------- 130--------- 121,9
0,0550---- 142,5------- 132--------- 123,8
0,0560---- 145--------- 134--------- 125,6
0,0570---- 147,5------- 136--------- 127,5
0,0580---- 150--------- 138--------- 129,4
0,0590---- 152,5------- 140--------- 131,3
0,0600---- 155--------- 142--------- 133,1
0,0610---- 157,5------- 144--------- 135,0
0,0620---- 160--------- 146--------- 136,9
0,0630---- 162,5------- 148--------- 138,8
0,0640---- 165--------- 150--------- 140,6
0,0650---- 167,5------- 152--------- 142,5
0,0660---- 170--------- 154--------- 144,4
0,0670---- 172,5------- 156--------- 146,3
0,0680---- 175--------- 158--------- 148,1
0,0690---- 177,5------- 160--------- 150,0
0,0700---- 180--------- 162--------- 151,9
0,0710---- 182,5------- 164--------- 153,8
0,0720---- 185--------- 166--------- 155,6
0,0730---- 187,5------- 168--------- 157,5
0,0740---- 190--------- 170--------- 159,4
0,0750---- 192,5------- 172--------- 161,3
0,0760---- 195--------- 174--------- 163,1
0,0770---- 197,5------- 176--------- 165,0
0,0780---- 200--------- 178--------- 166,9
0,0790---- 202,5------- 180--------- 168,8
0,0800---- 205--------- 182--------- 170,6
0,0810---- 207,5------- 184--------- 172,5
0,0820---- 210--------- 186--------- 174,4
0,0830---- 212,5------- 188--------- 176,3
0,0840---- 215--------- 190--------- 178,1
0,0850---- 217,5------- 192--------- 180,0
0,0860---- 220--------- 194--------- 181,9
0,0870---- 222,5------- 196--------- 183,7
0,0880---- 225--------- 198--------- 185,6
0,0890---- 227,5------- 200--------- 187,5
Beezer is offline   Reply With Quote
Old Today, 04:40 PM   #6
MidlifeRiding OP
Joined: May 2014
Oddometer: 12
I ran across that chart and a few other useful ones during my research.

One of the most helpful for working out deficiencies was this one -

And there was another good one too that I can't seem to find now that showed all of the different jets/valves/needles and what effects they have on the overall fuel delivery per throttle position.
Patrick Hayden's U.S.A. trip thread
My trip info, updated regularly - MidlifeRiding
MidlifeRiding is offline   Reply With Quote


Thread Tools Search this Thread
Search this Thread:

Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On

Forum Jump

Times are GMT -7.   It's 08:49 PM.

Powered by vBulletin® Version 3.8.5
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Copyright ADVrider 2011-2014