help with engine / carbs

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Beean123

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i was wondering if someone could tell me why the rightside pipe is hotter than the leftside,i just recently rebuilt the top half,new rings,gaskets,etc. i have taken the carbs off and cleaned, i noticed the mixture screws have a plastic cap on them,and when it does start it hits on the leftside and not the rightside, and then when it does the motor will rev up and i have to hurry and kill the motor:banghead:
 
If you haven't removed the idle mixture screws you haven't cleaned the carbs yet. What year? I can't remember which, if any? XS650's have plastic idle jet caps. Go to tech at the top of any XS650 page then carburator follow one of the guides all the way skipping NOTHING. A few parts generally need to be replaced to get properly functioning carbs. Don't feel bad, seldom is the first carb overhaul the one that that fixes the problem. Finally, no amount of carb overhauling will cure an ignition problem. Are your valves and cam chain tension set to specs?
 
They all run hotter on the right side. Some attribute it to air flow, most to the fact you just have alot more on that side that heats up. A 15-20 degree difference is common.
It sounds like a vacuum leak with the high revving.
Your carbs are the 78-79 38's with the mix screws coming out the side.
If it were me and the carbs were really nice I would be tempted to clean them and put them up on the chance someone doing a restore would want the stock carbs with the plastic covers intact.
Find a cheap pair of 34's (80-81) with the side pull choke and tune them with new jetting and canadian needles.
 
the bike is a 1978,yamaha says it a'79, i have disassembled the carbs,socked them and checked the float level,i have replaced the cam chain guides and adjusted the tension,as far as the valves their set to specs, i have replaced the points with a pamco electric ignition from mikesxs.com, now, it does start up better with the,i bought the complete ignition with coil,wires,etc.now, i have not replaced the rubber boots the the carbs mount into on the intake side,i have some oil leaks were the oil tube and the chain tensioners on the front side of motor,i just picked up the copper washers for them, is there anything i need for the threads
 
sorry, i meant soaked the carbs and reassembled them, now, the repair manual states the carbs settings are preset, the air/fuel screws have small plastic caps which have tabs that keep me from turning them, we took them off so we could adjust the screws
 
I would run it for a few minutes with the RH not firing and pull the plug. it it's dry an intake leak or plugged idle circuit is likely. If it's wet a float or float valve issue is a place to look. Could easily be both! Have you checked compression? How have you synched the carbs?
 
sorry, im meant soaked the carbs, ha ha. yes i have checked the copression its rite up there around 100 psi. would you happen to know how to get the clip back on the master lick for the drive chain
 
From the end then a slip joint pliers to finish up, the offset of the jaws helps you pop it on. It is important that the open end faces away from the direction of travel. Used clips are dangerous. A lot of guys refuse to use a masterlink at all. They are probably the smart ones.
 
okay, thank you for your time, i might just take this to a shop to have it checked out and hopefully be able to ride. im not good with carbs, the rebuild went good.
 
Carbs aren't really hard, just fussy, time consuming and tedious. :laugh:
Good luck and keep at it, you'll get it.
 
"Right up there" should be around 150 lbs. 100 is considered low, very low in fact. Maybe you performed the test incorrectly. Do it on a warm engine and hold the throttle wide open while cranking to get best results.
 
hello, i was just wondering, when i go to measure the float level,do i do it with the gasket in place or with the gasket removed, and do i measure it from the inside lipwhere the gasket would be to the top of the float
 
Measure without the gasket, from the flat part of the sealing surface. Not up on the ridge. Also hold the float at the point the float arm just touches the pin on the needle without compressing the pin.
www.amckayltd.com/carbguide.pdf is a great read.
 
Last edited:
Hello xsleo, i just rebuilt the top half,i just did a compression check and i got about 120 psi, is that good and will it get higher as the rings seat?
 
After a top end re-build, 120 psi is poor. You should be getting at least 140 psi.

Is your gauge reliable? Borrow a gauge from a friend to confirm. Is the throttle being held wide open? The best way is to use the starter motor (if you have one)to crank the engine. If kicking you may need to kick it 8 to 10 times to build pressure.

Do you have correct valve clarances...............this ensures the valves are fully closing. Did you lap the valves when you did the overhaul?
 
The book calls for 145 psi. Did you hold the trottle wide open while doing the compression check? Holding the slides up won't hurt either. Warming the engine up helps too.
The compression might come up a few lbs as the rings seat in. On my second over top end with the engine full of assembly lube, in the engine stand, no carbs I got about 165 psi. After I ran it for a few miles, about 50, it got the assembly lube worked out and the compression settled to about 150, warm engine throttle wide open.
I ran it for about a year and decided to do the 750 kit. I should have checked the compression before I tore it down.
 

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