Am I too big? Or is my XS underperforming?

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buffaloborn

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Hey.

Anytime I take my bike out, and get her on an open road where I can really let her go, she usually just peaks out at 70-75 mph. When I'm in fifth on a relatively flat road, and I try to go over 4000rpms, she just starts shuddering and hesitating, and won't make it much faster than 70-75.

I am a 6'4" 270lb guy though. Am I just expecting too much out of a 30 year old 650cc machine that produced 42 rwhp?

What kind of speeds are you guys getting, snd how big are you?
 
If you're too big for it, it might not go as fast as it should but I think it would just stop going faster without the hesitating and shuddering. You might need to do some tuning. Are you currently in Buffalo? I'm in the South Towns. Drop me a P.M. if you are local and maybe I can help you out.
 
I'm 280+ and mine will get up over 75 without stutter. The front end shuttering is a different story though.
 
Stock?? Exhaust mods? Air filter mods? Year? What ignition? What maintenance has been done? Otherwise it's kind of a my motorcycle don't run how do I fix it question?
My stone stock 83 readily pulls to 85 90MPH with more available. I'm 6' 3" 170lbs. weight doesn't make that much difference to speed on the flat. It's about wind drag.

Oh
Am I too big? Or is my XS underperforming?
Yes and Yes.
 
115 down hill 185 5' 10'' You shouldn't be spiting an sputtering. Wind restance and weight will hurt your top speed. I would stay away from under gearing 18 and 30 ect. keep the stock 17 and 34. You are not going to be able to redline in 5th geared right you should be able to get 6000RPM flying mile no spiting and sputtering it just won't go any faster. Work on it your not there yet.
 
Stock air filters. Stock carbs. Exhaust is stock, but the previous owner drilled 4 holes in the baffles, and I don't know what's up with that.

Could it be the holes he drilled? Maybe the bike isn't tuned to accomodate those? I don't even know why the holes were drilled in the first place. I'm fairly new to motorcycling.
 
buffaloborn,

Here is a list of things that can hold you back:

Bike goes slow (< 80MPH)

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 80 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 wheels.
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 (too rich) or hole in air filter (too lean)
28. High altitude
29. Very hot air, like 95+F
30. Very cold air, like 32F
31. Low oil (hot engine, engine friction)
32. Really dirty oil (engine friction)
33. Gas in the oil (engine friction)
 
pamcopete said:
buffaloborn,

Here is a list of things that can hold you back:

Bike goes slow (< 80MPH)

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 80 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 wheels.
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
Click to expand...


THANKS PETE!!! I'm definitely overdue to change my plugs. Maybe I'll invest in some of those special plugs at MikesXS.
 
off topic. go buffalo!

same issue, will try the pods and gas cap fix. runs great til 4.5rpm, then shite. raised needle, larger jet, non-vacuum petcocks. still same problem, will report back after tests.

Morgan
 
At 4K the engine only makes about 25 HP, so yeah you're underperforming. Missing half the fun right there. For the record my rd200 does 75.
 
I'm 6' tall, in the 210 lb range. I've gotten my xs650s up to about 95 mph. Could probably go faster, but... I'm Chicken.
 
buffaloborn,
You've had a offer of help from one of the best tuners on the board.
He is local to you, even if he wasn't the education you could get would be worth the expense .
Best advice I got is.
Forget the public forum and pursue it.
 
Pulled the old pods that came with the bike. Problem resolved! As I read early, cheap filter blocking intake ports on carb mouth. Thanks everyone.

M:thumbsup:
 
Pete, what is running excessive octane supposed to do? Make your wallet thinner? I don't get that one. The gas costs more, but there is NO performance advantage unless the engine needs that level of octane. These small cylinders and low compression should never need anything above the 85-87 family, unless modified. Am I missing something?
 
On the inside of my 81's side covers there is a chart giving the requirments of the bike. On it it lists fuel as a minimum of 91 research octane. Most places around me don't sell 91 octane gas. 87, 89, 93 are the options. So with a 91 minimum what should I run? Low octane reduces performance, increases detonation. Knock to some folks. Knock can lead to piston damage and a costly rebuild. The few cents more for the 93 is cheap insurance against engine failure.
Leo
 

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