72 SL 292 carb adjustments

corman007 · Jan 22, 2008

Does anyone know the factory settings for the 72 SL292. We rebuilt the carb last night and can't seem to get it running well. Had both the adjusting needles out to replace the o-rings.

Has two adjusting screws on the clutch side of the carb? Any help would be great. The more we play the worse it gets.

Old Man · Jan 22, 2008

What type of carb is it? From the limited info I have, it should be a Mikuni BN38-34 (Mikuni Diaphragm)If so there should actually be 3 adjusting screws (2 on the left side and one on the right) The top one on the left that sticks straight out (90 degrees) is the High Speed Adjusting screw. The other one on the left that angles downward is the idle speed adjusting screw. The one on the right that sticks straight out is the Idle Mixture adjusting screw.

The initial setting for the High Speed screw is 1 1/4 to 1 1/2 turns out from a gently closed position. The initial setting for the idle mixture screw is approximately 1 1/4 turns from gently closed. Fine tuning of these setting should occur after the engine has reached operating temp. The idle speed screw should be adjusted to obtain 1300 rpm at idle. Clockwise adjustment of the two mixture screws will lean out the mixture, counter clockwise will richen it.

corman007 · Jan 22, 2008

Thanks

Thanks for the info. I'll take a pic of the carb and post it. It only has 2 screws on the clutch side. both sticking straight out. The one in the front is small and the one clsest to the driver is larger. The only other adjusting screw is on the bottom of the carb. On the diaphragm housing. It points straight down. and the idle screw of course. It is a Mik. though

Old Man · Jan 22, 2008

Are you sure it's a Mikini and not a Keihin Diaphragm carb? From your description it sounds more like a Keihin CD42-38 which was used on the GP292.

If it's a Keihin Diaphagm, the fuel level needs to be set as well. That's what that bottom screw is for. There should be a sight tube on the left hand side and when the motor is running at idle the fuel level in that sight tube should rise to the level of the bottom gasket of the upper fuel pump cover. If it needs to be adjusted, loosen the lock nut on the bottom adjusting screw and turn in to raise the fuel level or out to lower it. When it's set at idle speed, raise the back of the sled and check it at 3000 RPM . The fuel level should not change in the sight tube.

Set the idle mixture at 1 1/4 turns from gently closed (smaller front screw) and the high speed at one turn from gently closed. Adjust again as operating temp is reached. Set you idle speed at approximately 1300 rpm.

corman007 · Jan 22, 2008

just checked and it is a Keihin

Old Man · Jan 22, 2008

Just edited my 2nd post. Added setting for Keihin carb.

corman007 · Jan 23, 2008

I think my other problem is the oil injection is working sporadicly. Yesterday I had very little blue smoke. Thought it was because it was running out of tune or just better than before the carb rebuild. Today no smoke? Can I just take the oil injection out and mix my gas? I don't trust the 35 yr old injection any more. Even if it's convenient. Thanks for the carb help. I appreciate it "Old Man"
I's been years since I have worked on these old machines. I have a race against a coworker and his poor running 300 Moto-ski. I hope to have mine running for sun.

Old Man · Jan 23, 2008

I've heard of that being done before. I guess premix is better than questionable oil injection. The only question is what ratio 20:1 - 40:1 ?:dunno:

corman007 · Jan 23, 2008

I think with todays oils 40:1 is safe. I run 50:1 in all my two stoke toys and it has never failed me.

I doubt I can find parts for the old injection system on the 292. Heck I have never seen another SL292C before. Lots of GP's and 292B's

Since the highest unleaded octane around here is 94 and far less than the leaded fuel I should be ok with 40:1-50:1

This Yamaha amazes me! It's 35 years old and has had nothing but a few belts,chain and a track and thats it. It usually starts on the first pull. I'm scarred to rebuild it. I fear it just won't be the same. Unless I find an 80yr old master mechanic lol.

Old Man · Jan 23, 2008

Hell, I'm almost 50 and I still run:laugh: You should throw a photo in to vintage sled of the month.

corman007 · Jan 23, 2008

I plan too when I get it all back together. I'll take some race action shots LOL

RJ Gleason · Jan 23, 2008

Watch the plug color to determine if it is running correctly. It is extremely rare that the oil pump goes bad. Keep an eye on the oil tank as well to be sure that it is using the oil.

corman007 · Jan 23, 2008

I disconnected the pump today and mixed the gas about 35:1 and it purrs like a kitten. Now I just need to take the old beast out for a test and tune run. Thanks for your help gentlemen:thumbsup: :thumbsup: Nice to find some help on this great forum. I'll post some pics of the beast soon.

corman007 · Jan 24, 2008

Well boys I give up. The old beast will idle for a few min. and thats it. touch the throttle and it dies. I can't believe how touchy it is. It ran fine and then the fuel pump on the bottom of the carb was rebuilt (3 times now). I used new parts the first and 3rd time. It just wont run any more. And no shops in my area will touch it. Anyone have a better carb I can throw on this?

Old Man · Jan 25, 2008

Try adjusting the fuel level up until it's level with the upper gasket surface of the fuel pump cover. It's worth a try.

corman007 · Jan 25, 2008

I tried that for hours last night. Either no fuel is visible or it overflows. I love old sleds but man can they be a pain in the rear. I'm pretty handy but this thing has me stumped.

corman007 · Jan 26, 2008

Well here is the beast.Just a cell phone pic but you get the idea.

72 SL 292 carb adjustments

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