Engine revs high in all gears

[Setroc]

Hey guys,
Need some help with my 80 xs. Bike starts and runs. The problem is that once you're in gear, any gear, the engine plateaus and all you get is the engine revving high (me accelerating). For example in first gear she'll accelerate to 10 mph then plateau. At this point I'll drop it into second gear accelerate fine briefly but then quickly hit that plateau again. Same thing for third gear and so on. I rebuilt the top end this past winter. Everything feels, sounds good. I cleaned out my carb just because it was sitting but made no changes to it's setup. I'm running mikuni vm34s with a 45 pilot jet, 45 needle jet, 145 main jet, 135 air jet, a 6 slot needle, long open exhaust pipes and mikes xs pod filters. Bike ran fine with this setup prior to rebuild so I figure it should run fine now. Reading/diagnosing my problem on this site I know I have to make some changes to this entire setup but first things first. I can't figure out why the engine is plateauing. Any help would be greatly appreciated. Thanks in advance.

 

[peanut]

if there is no coughing or spluttering backfiring etc I'd guess it could be timing related.
Not much info ..... have you checked the timing TDC etc and advance
A video with sound sure would help

 

[gggGary]

+1 Advance curve or lack there of comes to mind.

 

[Setroc]

Peanut, Gary sounds like you guys were pointing me toward a timing issue so I was trying to research as much as I could to give as accurate a picture as I can concerning my problem. I'll be honest. I'm lost. I've never had a timing issue. It seems like I've dealt with everything else but that. Anyway, I took some videos of the bike running per request. Hopefully it will give a better description then I can. Btw, peanut, no points, no pamco, all original electronic advance. Be patient, guys. I'm going to try and post my videos.

 

[gggGary]

That narrows it down pretty fast. This will seem strange but disconnect your voltage regulator and go do a quick run see if it will rev. Next do a search on testing pickups ohm them out. both gray and orange to black should give you about 650 ohms.

from the manual via XSLeo

Testing the pickups is done by using an ohm meter. The pick up has three leads. Grey, orange and black wire. check the ohms from the black wire to the other two wires. 80-81 should be 550-850 ohms, 82 up 630-770 ohms.
If these test on yours is good then your pickups are fine.

It also could be something about the taper jet, slide, main, the slides start to lift at about that RPM.

This type of trouble shooting is about testing and eliminating, once you are SURE something is right you can cross it off the suspect list.

 

[scabber]

The TCI controls the timing advance. They do go bad. A timing light will tell you if it is working correctly or not.

 

[Setroc]

Guys, trying to load these vids but not happening. I'm listening to what you're saying. keep the advice coming.

 

[scabber]

A slipping clutch will cause high Revs. Have you adjusted it.

 

[Setroc]

Guys, finally figured it out and put them on YouTube. In video 1 I shift from neutral to first. Just trying give you guys an idea of the plateau. I think the second video is better because I run thru to the fourth gear and you can hear said plateau. Here's the second video.

Scabber, bike shifts fine but I'll look into the clutch too.

 

[peanut]

wow I've never heard one run so badly Good videos

So many things it could be. It starts and idles fine and will rev slowly so I don't think it can be a fuel starvation issue.
I still suspect electrical or timing issue.

I can't see your battery ? are you running with a small gel battery or a capacitor ?

To eliminate the battery being the culpret, attach any 12v car battery with some jump/boost leads and try run it . is there any improvement ?
Try disconnecting the rectifier /regulator and all the fuses except the one that supplies the ignition and coils etc. Its clearly a diy loom so its difficult to know how its been constructed without a schematic.

Next I would check that the cam chain has been placed on the correct sprocket tooth. The cam sprocket alignment cutout needs to be at 12am with the piston at TDC

Beg borrow or steal a timing light and check the timing advance curve is correct .

 

[Setroc]

Sorry for the delay. I work nights and chauffeur my kids around all day it seems. Hard to find time to really dig into the bike. Anyway, I bought an ohm meter and a timing gun and have no real idea of how these work or experience with either. I've been reading lots so I do have references if need be but I'm still not sure how to adjust the timing on tci ignition. For example, let's say I use the ohm meter and get the correct voltages for my wiring and move on to find out, using my timing gun, that I need to make a timing adjustment I still don't know what I'm physically adjusting. Am I moving the rotor assembly? The pick up coil? The brushes? All of them? No idea. I found plenty of info for adjusting point systems and pamco systems but none for tci systems. Will I have to take the top end off again and start from scratch? This is what I'm afraid of.

 

[gggGary]

The pick ups move on the stator 82-83, they are held by no remove screws on the 80-81s the screw head can be slotted to loosen them. but basically the TCI does not go out of time.
Remove the round cover behind the shift lever hook up your timing light, watch the timing mark on the rotor as you idle and rev, you should see the timing advance to max at about 3,000 RPM.
This thread explains it well

http://www.xs650.com/forum/showthread.php?t=42687

 

[gggGary]

TCI module is shot. Engine isn't getting any advance in timing.

Maybe.

I'd be doing that timing test.

 

[Setroc]

So I ordered a replacement reg/rec and ignition box and tried them both out. I followed Gary and peanut's suggestion and left the reg/rec unplugged and lo and behold the bike runs like a champ. Bad pickup coil? Still haven't tested them with ohm meter. I bought 2 ohm meters, one digital the other has a needle. Still sifting thru but very excited that after so much time spent, whenever possible, I might actually lick this and get her running yet.

 

[gggGary]

That points at a weak ignition magnet on the rotor. Lots of threads for a cheap, easy fix for that problem.

 

[peanut]

So I ordered a replacement reg/rec and ignition box and tried them both out. I followed Gary and peanut's suggestion and left the reg/rec unplugged and lo and behold the bike runs like a champ. Bad pickup coil? Still haven't tested them with ohm meter. I bought 2 ohm meters, one digital the other has a needle. Still sifting thru but very excited that after so much time spent, whenever possible, I might actually lick this and get her running yet.

well done its great to have the satisfaction of fixing something yourself .
Sounds like you'll be going out on a shakedown run real soon

 

[madjap]

Hey S2R, explain that to me. No advance would make it rev TOO high? I would think it wouldn't want to rev at all...? Dumb it down if you wouldn't mind, but why would it do that? thanks

 

[XSLeo]

Ok, The TCI uses a signal from the pickups. The pickups are triggered by a magnet mounted in the rotor. The TCI uses these signals to tell when to spark.
Now as a magnet ages it gets weak. The rotor when has a very strong magnetic field when charged. This strong magnetic field can cover over the weak magnet. This prevents the pick ups from getting a good reading of the magnet.
Poor reading = poor running.
This is proven by the bike running great with the reg/rec unplugged. With the reg/rec unplugged the rotor gets no charge, the pick ups reads the magnet just fine.
To fix you need to add a new magnet on top of the old one Radio Shack sells a pair of rare earth magnets for $2.99. Item #64-1895, these are 3/16 inch/4.5 mm in diameter. Use a good epoxy glue, I like JB Weld, Glue this new magnet onto the old magnet.
Been done plenty. Works great.
Leo

 

[XSLeo]

Another thing, does the charging system work? On my 81 when the charging system wasn't working very well the battery would get low and the bike would idle ok but not take throttle.
Check your charging system as well.
Leo

 

[Setroc]

Guys, jb welded radio shack magnet on rotor and she's up and RUNNING. Now if the weather would cooperate I could get a better feel for how well the fix took. It's been raining, or snowing or both for the past week. For now I, we, can claim victory and celebrate with revels. Thanks all for the help!