Won't go above 60mph?!

rafbobber702

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Hey guys, I have a 79' xs650 bobber. Today was my first time taking it on the freeway since I've owned it. I been cruising on local streets to brush up on my riding skills.

So when I get to 5th gear on the freeway, soon as I get to around ~60mph it starts cutting out like it's hitting the rev limiter "ta ta ta ta..". And it won't go any faster! I ended up having to exit the freeway to cruise on the local street.


Does my xs650 have a different gear setup possibly? I know there isn't any mechanical/electrical issues since I just got it back from my mechanic who did a complete tune-up, inspection, new pamco ignition system, etc. And the bike runs smooth, aside from not being able to go above 60mph.

Any ideas? Or what to check for?

Thanks!
 

crazyorigin

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I would suspect the timing is off or the carbs need tuning. Do you have a tach on it? If not does it feel like it's hitting the maximum rpm's, or just breaking up in the middle of the RPM's? It would have to be geared way down to be maxed out at 60mph. It would feel like it was revving to the moon too I would bet.
 

rafbobber702

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I would suspect the timing is off or the carbs need tuning. Do you have a tach on it? If not does it feel like it's hitting the maximum rpm's, or just breaking up in the middle of the RPM's? It would have to be geared way down to be maxed out at 60mph. It would feel like it was revving to the moon too I would bet.

The carbs were cleaned and tuned as well during the full tune-up. No tach, and yes it feels like it's hitting the max rpm. There's no break up/hesitation during acceleration, it goes through all the gears smoothly and consistent.
 

crazyorigin

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Does it lurch like the clutch may be slipping? I am just kind of poking at things in the dark....

Was it running above 60mph before the "tune up"? Unless your mechanic is one amazing carb tuner, getting the carbs on something spot on takes a good but of trial and error. Jet it, go run the snot out of it, see how it feels, go from there is what I do. Not saying your mechanic messed anything up but sometimes "tune ups" need further tuning up when you get them back. It would have to be way out of whack to break up at 60 a bad it would stop there. Someone else will likely be more help.
 

NONclow

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Misspelled Prophylactic, OR
I just got it back from my mechanic who did a complete tune-up, inspection, new pamco ignition system, etc. And the bike runs smooth, aside from not being able to go above 60mph.

Any ideas? Or what to check for?

Thanks!

Dirty/restricted filter(s).... if any?
When it happens, open the fuel cap, if there is a woosh of air (being sucked in).... blocked fuel tank vent.
Open cap and retest... with a lower fuel level or rag in the hole to hinder splashing,
 

rafbobber702

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Does it lurch like the clutch may be slipping? I am just kind of poking at things in the dark....

Was it running above 60mph before the "tune up"? Unless your mechanic is one amazing carb tuner, getting the carbs on something spot on takes a good but of trial and error. Jet it, go run the snot out of it, see how it feels, go from there is what I do. Not saying your mechanic messed anything up but sometimes "tune ups" need further tuning up when you get them back. It would have to be way out of whack to break up at 60 a bad it would stop there. Someone else will likely be more help.


Don't feel any clutch slipping at least to me. Honestly I've had the bike sitting in my garage for the last 2 years. I was lazy to get it worked on, and it just needed to get the entire ignition system replaced. So just last month I finally got a brand new completely redone ignition system, oem plus aftermarkets from Mikesxs.

I had purchased the bike knowing it had an ignition problem. So it never really ran down the street, it would only start up and go for a few a minute or so before dying.

So yeah, I don't know if it ever ran over 60mph with the previous owner.

I have confidence that my mechanic knows what hes doing, etc. His shop specializes on vintage bikes from yamahas, triumphs, etc.

But honestly, everything on the bikes runs smooth to me. It accelerates through every gear smoothly on the streets.

I have no idea what's up with 5th gear no going over 60mph. Maybe it's running a different sprocket?
 

rafbobber702

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Dirty/restricted filter(s).... if any?
When it happens, open the fuel cap, if there is a woosh of air (being sucked in).... blocked fuel tank vent.
Open cap and retest... with a lower fuel level or rag in the hole to hinder splashing,

The air filter, and the filters on the carbs were cleaned up as well.

I've opened up the fuel cap many times while the bike was running never heard any kind of suction of air or sounds that you speak of.
 

NONclow

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Not while it's running. After it stumbles, stop when safe, shut off, THEN open cap.

Also, after incident/stumble/issue, test ride with the cap open.....
 

rafbobber702

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Not while it's running. After it stumbles, stop when safe, shut off, THEN open cap.

Also, after incident/stumble/issue, test ride with the cap open.....


I see, like purposely letting it shut off in gear while stopped, then open cap?

I honestly haven't had any stumbling issues, except for when I don't give enough gas and release clutch and the bike dies. That's the only issues I've had since I been riding it.
 

crazyorigin

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I would check for any loose connections in the ignition plug ins. I haven't installed one yet but I have seen people have issues with pins not being soldered inside the plugs to the wires, it could be causing a break in the signal to the ignition and causing it to go retarded or advanced. Count your teeth on the rear sprocket and if you can pop off the left side cover and count the teeth on the front and let us know that will answer the gearing part of the question easily.
 

rafbobber702

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I would check for any loose connections in the ignition plug ins. I haven't installed one yet but I have seen people have issues with pins not being soldered inside the plugs to the wires, it could be causing a break in the signal to the ignition and causing it to go retarded or advanced. Count your teeth on the rear sprocket and if you can pop off the left side cover and count the teeth on the front and let us know that will answer the gearing part of the question easily.


Plug wires and plugs are brand new. And Ive double checked them already too, don't see any issues.

How many teeth should the front and rear sprocket have? I can't really count the rear sprocket since the chain covers half the sprocket.
 

crazyorigin

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Put a dot on one tooth with a paint marker or wax pencil, or even mark it with a small piece of tape below where the chain rides, pop the bike on the center stand and turn the wheel while counting the teeth. I think stock gearing is 17/34. If the sprocket has been swapped some companies stamp the number of teeth on the side of the sprocket.
 

rafbobber702

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Put a dot on one tooth with a paint marker or wax pencil, or even mark it with a small piece of tape below where the chain rides, pop the bike on the center stand and turn the wheel while counting the teeth. I think stock gearing is 17/34. If the sprocket has been swapped some companies stamp the number of teeth on the side of the sprocket.

I just counted the rear sprocket. I did it 3 times to be sure, and it has 34T. I couldn't count the front sprocket due to lack of enough tools.
 

peanut

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You can't jet and tune a bike in a workshop it needs to be done under load on the road or dyno.

This could be an electrical or fuel related issue , there is insufficient information to tell.

Did you check to see what colour your spark plugs are after a high speed run?
That will tell you if you have a fuel mixture or fuel delivery problem or not. Its always the first thing you should check as its easy and its diagnostic

If the air filters have been changed to pods it is possible the bike is running too lean which is very bad for your engine


Its unlikely to be anything to do with your gearing.

Check your spark plugs for colour (post a picture.)
Check the fuel flow rate to the carbs (see handbook)
Check the voltage of your battery after it has been cutting out ,(low volts will cause this problem and is a high possibility)
Check your timing and advance You haven't told us if you are running points or electronic ignition ?
Check and clean grounds and make sure there are no electrical shorts
Try substituting some good coils plugs leads etc

If the bike is starting and running that well it can't be anything major
 

pamcopete

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Bike goes slow (< 60MPH)

1. Low battery / charging system. A low battery will produce a low ignition voltage at the plugs which is most evident at higher RPM's.
2. Timing. Did you use a timing light to set the timing?
3. Stuck or no advance. When checking the timing with the timing light, did you check for maximum advance at 3,000 RPM.
4. Binding advance rod. Check out this video:


5. Fouled plugs. Did you install new plugs? Check them after you got it running?
6. Plug wire not making contact in the coil. Measure the resistance from plug cap to plug cap to ensure that both plug wires are making contact in the coil.
7. Brakes dragging.
8. Speedo out of calibration. You are actually going faster than 60 MPH! Use your GPS to check the speedo.
9. Tire pressure. Pump up to 32 PSI for high speed.
10. Drive chain too tight. That will rob you of power to the rear wheel.
11. Enricher plunger stuck partially on.
12. Enricher (choke) left on or partially on.
13. Weak or loose advance springs. Weak or loose advance springs cause the advance to use up some of the available movement because you have to essentially retard the advance to get it on the idle advance mark, so there is less movement available at higher RPM's.
14. Timing chain needs adjustment.
15. Cheap or bad gas.
16. Low octane gas.
17. Water in the gas.
18. Partially blocked pet cock or fuel filter.
19. Paper filter that has low flow when the tank is not full.
20. Try a run with a full tank of high octane, fresh, expensive gas.
21. Blocked fuel cap vent.
22. Incorrect sprockets. What RPM are you getting at 60 MPH.
23. Rear tire rubbing on brake rod or swing arm.
24. High wind resistance. Are you a large person?
25. Throttle cable not fully opening the throttles.
26. Blockage in the muffler(s)
27. Dirty or blocked air filters
28. High altitude
29. Very hot air, like 95+F
30. Very cold air, like 32F
31. Low oil
32. Really dirty oil
33. Gas in the oil
34. Weak TCI magnet in rotor. Unplug Reg/Rect to test
35. Cracked carb boots.
36. Hole in carb diaphragm(s)
37. Cheap pods covering air hole in carb inlet
 

rafbobber702

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You can't jet and tune a bike in a workshop it needs to be done under load on the road or dyno.

This could be an electrical or fuel related issue , there is insufficient information to tell.

Did you check to see what colour your spark plugs are after a high speed run?
That will tell you if you have a fuel mixture or fuel delivery problem or not. Its always the first thing you should check as its easy and its diagnostic

If the air filters have been changed to pods it is possible the bike is running too lean which is very bad for your engine


Its unlikely to be anything to do with your gearing.

Check your spark plugs for colour (post a picture.)
Check the fuel flow rate to the carbs (see handbook)
Check the voltage of your battery after it has been cutting out ,(low volts will cause this problem and is a high possibility)
Check your timing and advance You haven't told us if you are running points or electronic ignition ?
Check and clean grounds and make sure there are no electrical shorts
Try substituting some good coils plugs leads etc

If the bike is starting and running that well it can't be anything major


I'll have to check the spark plugs and see what color I see.

The air filters are the round flat type, I assume those are still pod filters? These were cleaned from my understanding, might have to get that double checked.

Battery is brand new, along with new electrical wiring all around, and new ignition system. New coils, new plug wires, new plugs, etc. And from what I remember the bike was a points ignition.
 

rafbobber702

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Try reading some of the threads found using the search term "reversion", and see if anything sounds familiar. For example:

http://www.xs650.com/forum/showthread.php?t=26938&highlight=reversion
http://www.xs650.com/forum/showthread.php?t=27927&highlight=reversion

Cool, so after reading those 2. Looks like I'll have to do the same. I do run short pipes that open up right under the foot pegs, I'll head to the autopart store and clamp on longer pipes to see how it works. It would just be temporary until I get a GordonScott exhaust. And I don't have uni-air foam filters as mentioned there, I'll have to get that as well.

This is the type of air filter I currently run on the carbs.
KandN-RC-0330-filter-1.jpg
 
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rafbobber702

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Bike goes slow (< 60MPH)

1. Low battery / charging system. A low battery will produce a low ignition voltage at the plugs which is most evident at higher RPM's.
2. Timing. Did you use a timing light to set the timing? Not mechanically inclined to do that unfortunately, ill have my mechanic to check that out
3. Stuck or no advance. When checking the timing with the timing light, did you check for maximum advance at 3,000 RPM.
4. Binding advance rod. Check out this video:


5. Fouled plugs. Did you install new plugs? Check them after you got it running? I'll have to check that out, what color should they be?
6. Plug wire not making contact in the coil. Measure the resistance from plug cap to plug cap to ensure that both plug wires are making contact in the coil.
7. Brakes dragging. Brakes feel fine to me, no drag
8. Speedo out of calibration. You are actually going faster than 60 MPH! Use your GPS to check the speedo. NO speedo/tach. I use the GPS Speedo App on my Phone to calculate speed. And the issue arises when I reach ~60mph
9. Tire pressure. Pump up to 32 PSI for high speed. PSI is at around 30-31
10. Drive chain too tight. That will rob you of power to the rear wheel. Don't know
11. Enricher plunger stuck partially on.
12. Enricher (choke) left on or partially on.
13. Weak or loose advance springs. Weak or loose advance springs cause the advance to use up some of the available movement because you have to essentially retard the advance to get it on the idle advance mark, so there is less movement available at higher RPM's.
14. Timing chain needs adjustment.
15. Cheap or bad gas.
16. Low octane gas.
17. Water in the gas.
18. Partially blocked pet cock or fuel filter.
19. Paper filter that has low flow when the tank is not full.
20. Try a run with a full tank of high octane, fresh, expensive gas. I only run 91 or 93 oct fuel, in Los Angeles I have 91oct
21. Blocked fuel cap vent.
22. Incorrect sprockets. What RPM are you getting at 60 MPH. I counted 34T in the rear sprocket, but couldnt check the front since I didnt have enough tools
23. Rear tire rubbing on brake rod or swing arm. Nope
24. High wind resistance. Are you a large person? Right now I'm just at 200lb, typically I'm like 170-180lbs. I gained weight the last few months. Haha
25. Throttle cable not fully opening the throttles.
26. Blockage in the muffler(s)
27. Dirty or blocked air filters
28. High altitude
29. Very hot air, like 95+F
30. Very cold air, like 32F
31. Low oil
32. Really dirty oil
33. Gas in the oil
34. Weak TCI magnet in rotor. Unplug Reg/Rect to test
35. Cracked carb boots.
36. Hole in carb diaphragm(s)
37. Cheap pods covering air hole in carb inlet


I've always noticed the fuel line on just the left side of the gas tank's petcock has a slight kink. Fuel seems to flow through smoothly, but obviously I can't watch it while riding. Everytime I turn on the petcock fuel runs down the fuel line normally, or so I think.

Could this be an issue? Everything on the bike has been running good and smooth since I got it back from my mechanic, I honestly don't have any complaints except this.

All the other technical stuff you mentioned, I'd have my mechanic check on that. And I lack a lot of tools since they're not at my house at the moment, or I'd be able to do more of those diagnostics your mentioning.


Here's a pic for reference;
20140905_174151_zps98a66847.jpg
[/URL][/IMG]
 

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TwoManyXS1Bs

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Cool, so after reading those 2. Looks like I'll have to do the same. I do run short pipes that open up right under the foot pegs, I'll head to the autopart store and clamp on longer pipes to see how it works. It would just be temporary until I get a GordonScott exhaust. And I don't have uni-air foam filters as mentioned there, I'll have to get that as well.

A quick and cheaper test would be to blast up to 70 mph in 4th gear, then upshift to 5th gear. That'll get you past the 'reversion' zone. If you find power returning at 70 mph and beyond, then it's probably reversion.
 
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