Keihin Base-line settings?

unclesol

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I am still trying to "sort out" the POs versions of tuning, so I can get my 79 running correctly, and I have found a few interesting approaches to things, such as tie-wraps around the clutch and throttle cables, pulled so tight that movement of either also moves the other. Also, the clutch cable was so tight against the left-hand choke, that every time you pull the clutch lever, it would also activate the choke, making it run way too rich (read black smoke, and blue pipes!).
All of the cables have been "released" and nothing is binding on anything anymore, but I think the PO had been playing with the jetting, trying to overcome the problems he didn't realize he had created in other ways. So, I am now trying to figure out what the base-line settings (jet sizes and air/fuel mixture screw) are for the Keihin carbs, that look like the XS Performance carb kit from Mikes (XS650Direct here in Canada). See following:

IMG_0906.jpg


FYI, I have installed a Boyer Bransden ignition kit, and have re-set the valves to correct specs already, so all other systems should be OK.
Lastly, can you confirm whether turning the idle adjustment screw in or out should be raising the idle speed, as right now I don't get any response in either direction, but I think that may have been caused by the inadvertent choking...
Any help would be greatly appreciated!
 
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There have been two intense threads about these carbs.
I'd suggest starting with mrriggs thread then the others.
 
I have read through mrriggs thread, and it is very helpful, but it didn't provide the "original" settings. I will probably end up where he did (my engine is currently very similar), but I would like to know where it is supposed to start from.
Thanks!
 
unclesol,

1. Start with main jet 9062 which is a #125. Slow jet 9042, #35. You may end up with a main jet 9061 #120.

2. Adjust idle mixtures to 1 1/2 turns out. Don't try to even out the idle with the mixture screws. See step 5 instead.
3. Turn idle speed screws all the way out and then screw back in until the slide just starts to move.

4. Open the throttle until one of the slides reaches the top of the throat, then adjust the other cable to match it.

5. Start engine and remove one of the vacuum blind plugs. Adjust the idle of the other carb for 900 - 1,000 RPM.
6. Replace the vacuum plug and do the same with the other carb.
7. Finish by connecting the two vacuum barbs together with a length of vacuum hose.
 
Unbelievable frustration!:banghead:
I must have been dreaming. I can't keep the thing running for more than about 10 seconds, and when I try to re-start it, it is backfiring like crazy!
I have taken the throttle cable and re-routed it directly across the top of the engine, so there are no hang-ups there whatsoever. I have set-up the carbs, as per Pete's suggestions above.
I have double checked the timing on the BB elec. ignition, and it seems to be spot-on.
The PO told me that nothing had been done to the inside of the engine, but I'm not sure what to believe. Both pistons are at TDC together, so the crank has not been re-phased.
I'm wondering if the cam chain may have jumped a tooth at some point?
I guess I'm grasping at straws, so any suggestions would be greatly appreciated...
 
Talk about deja vu. What you are describing is exactly the same as what I went through with these carbs. The bike was running so unbelievably bad that I didn't know where to start.

The first indicator was black spark plugs. Screwed in a new set and it ran better for a brief time until they fouled out again. That is a good sign that the carbs are too rich. I went through several sets of plugs while dialing down the carbs. Even went to a hotter plug at one point to help prevent the fouling. Hotter plugs are not a solution, just a stop-gap measure to keep the bike running long enough to tune it properly.

For me, the solution was bigger diameter jet needles. Step-by-step I worked all the way up to the largest diameter (leanest) needles and it runs pretty well. Going to the next leaner slide cutaway would probably cure it, but they are expensive and it runs well enough with just the fatter needles. With these carbs, almost all of the tuning is done with the slide needles, either changing diameter or changing clip position.
 
Does anyone know if Hiedens and MikesXS have altered the set up on these since they introduced them? because it's clear that plenty of folks have had to mess with them quite extensively to get them to run right and they market them pretty much as a "bolt on and play" modification.

I'm not in the market for a set, just curious to see if the suppliers are reacting to feedback.
 
Thats one thing about most modifications. Very few are "bolt on and play".
Most need some adjusting to get right.
Leo
 
Baseline settings for carbs used and/or developed in Europe (like these) many times don't work here in the states. I think maybe they have different gas formulations or something over there. Another example of this is that Heiden needle kit MikesXS sells. Reports are that it barely works at all here.
 
Talk about deja vu. What you are describing is exactly the same as what I went through with these carbs. The bike was running so unbelievably bad that I didn't know where to start.

The first indicator was black spark plugs. Screwed in a new set and it ran better for a brief time until they fouled out again. That is a good sign that the carbs are too rich. I went through several sets of plugs while dialing down the carbs. Even went to a hotter plug at one point to help prevent the fouling. Hotter plugs are not a solution, just a stop-gap measure to keep the bike running long enough to tune it properly.

For me, the solution was bigger diameter jet needles. Step-by-step I worked all the way up to the largest diameter (leanest) needles and it runs pretty well. Going to the next leaner slide cutaway would probably cure it, but they are expensive and it runs well enough with just the fatter needles. With these carbs, almost all of the tuning is done with the slide needles, either changing diameter or changing clip position.
I have had exactly the same issues re: plugs as well!
Any other mods to your engine? Other than the ignition, carbs and 2 into 1 (changing this to Omars Half-mile pipes shortly) mine is basically stock.
What jets did you end up with, and what position for the clip? And where is the best source for them?
Thanks for the help!
 
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