Engine wont rev above 3000rpms

[awoz87]

i have an 82 xs650 and when i first got it it had a leaky valve seal, it would not rev above 3000rpms at that time but i figured im tearing the motor down why worry about it now. so i took the engine apart, new gaskets, new rings, new valves/seals, basically a solid refresh. i also cleaned/rebuilt the carbs.

now i have it all back together and it still wont go over 3k, its sounds like its about to die/bouncing off a rev limiter. i have had the carbs off twice and given them a good cleaning. still happening. any ideas? could it be ignition related?

 

[retiredgentleman]

Did you check that the carb diaphams were not leaking.

 

[littlebill31]

Retiredgentleman has a good point. The diaphragms, if torn, will cause this. Look on the air filter (back) side of the carbs. You will see 4 ports, 2 on either side, and an oblong one on the top. Raise the round slide inside the carb with your finger and cover the top, oblong port with your thumb. Keeping the oblong port covered, release the round slide. It should not move or move very slowly. If it just drops the diaphragm could be torn or not seated correctly. The diaphragm has a tab that needs to fit in the corresponding groove on top of the carb body.

 

[pamcopete]

Check your advance mechanism for binding. If it wont advance, it wont go past 3,000 RPM.

 

[Tech7]

82 wouldn't have come with an advance mechanism.

 

[pamcopete]

Tech7,

Right...what was I thinking?

With the TCI system, you could have a bad pickup that would not allow the TCI box to advance the spark, so check your advance to se if it is at full advance at 3,000 RPM.

Here is a pic of the full advance position which is not marked in the '80 to '83 models.

 

[awoz87]

diaphragms seem to be fine.

do i check the advance when the bike is running?

also, could low volts cause this? ie. bad alternator

 

[xjwmx]

do i check the advance when the bike is running?

Put a timing light on it and rev it and see where the mark on the rotor moves to. I think the most likely thing is badly tuned carbs, sputteringly badly tuned, but it's just a hunch.

 

[awoz87]

i have bs34s and have the mixture screws 3.5 turns out, thats standard right?

 

[xjwmx]

From what I've read that should be in the ballpark, if the jets are original. Also - it's essential that the float height be right. Measure from the surface the gasket sits on to the highest point on the round area on the float, with the carb upside down. It should be 22mm +- 1. It's critical. If the gasket is stuck to the body side, add 1mm to your measurement.

Also, check your pickup. Either colored wire to the black should measure in the neighborhood of 700 ohms.

 

[xjwmx]

Also with the carbs, the float valve needle and seat have to be working and the o-ring has to be sealing. Otherwise it will run very rich or not at all. You can test the float valve by blowing in the tube and when you turn the carb upside down it should shut off the air flow. That tests for big leaks, anyway.

 

[XSLeo]

On the TCI ignition voltage is very important. I have an 81 with a bad charging rotor. If you unhook the reg/rec and fully charge the battery it runs very good, once the voltage drops It starts acting up. Backfires out the exhaust, sound like gun shots. Cutting out no power.
Start by charging the battery, then check battery voltage at idle and 3000 rpm.
Leo

 

[awoz87]

i have 750ohms for both readings on the pickup.

also, resistance between the white wires seems to be off. when i short my leads on the tester i get .3, when i do the tests between the wires i get .6, 2.6, 2.6 so that means .3,2.3, 2.3 bad stator?

the bike is an 82 so i dont believe i am missing something i need from my charging system, correct?

 

[nj1639]

Where's your brushes?

 

[awoz87]

thats the part thats missing huh? i honestly didnt know what they looked like. where would one acquire that part??

 

[xjwmx]

Good eye, NJ! LOL.

I think you might have to buy a stator on ebay to get the brush holder. Someone here might have one they'll flip you.

But - it sounds also like you have a bad stator. BTW, the value they give you in the factory manual should be doubled. The factory manual test gives you the resistance of one coil, but when you're reading between white wires, you're reading two coils, actually.

 

[awoz87]

http://cgi.ebay.com/ebaymotors/XS65...7124383QQptZMotorcyclesQ5fPartsQ5fAccessories

is that what i need?

 

[xjwmx]

Yes. But if you need a new stator, I've noticed they usually come with that part. You'll need a pair of brushes, too.

P.S. I noticed the one in that listing appears to come with brushes installed.

 

[gmiller217]

I noticed today Mikes has the brush holder listed separately ... can't remember how much though

 

[PRoberts317]

I had this same problem on my '83. Checked carbs, ignition, wires, plugs, timing, the whole 9 yards. Turned out my recently purchased alternator rotor (stator) was defective from the manufacturer. Changed that and she purred.