4k RPM / 60-65mph Top Speed?

[alfredo]

Ran the bike around town and it seems like she doesn't want to do any more than 4k or 65mph. I haven't tried to go more, but it gets really loud and starts to vibrate more than seemingly normal. Now, I don't necessarily want to do more than 60/65, but some speed limits are 70 where I am and I don't want to feel like I am going to blow the motor, just trying to do the rate of traffic.

It shifts perfectly, doesn't slip, starts and runs just fine. This is all after a fresh rebuild with 3rd oversize.

I am 6'6" and 230lbs. Could it just be me causing it to seem like it shouldn't go any faster?

 

[alfredo]

Also, I should note that this is in 5th gear at 4k and 17/32t sprockets.

 

[bloodthirstysystem]

you need to sync the carbs.

 

[alfredo]

you need to sync the carbs.

Not doubting you, just reiterating that it sounds like the motor is whining out. It's loud and rumbly and really feels like more of a mechanical limitation rather than bad fuel mixture. Could be way off though.

 

[shotgunjoe]

I have done 75+ 2up (total weight around 330lbs). Bike definitely vibrates more at higher rpm, and feels more sluggish 2up than riding alone, but never feels as though its gonna blowup.

What kind of exhaust are you running? Louder exhaust tends to make it seem like you pushing your engine harder than with a quiet one.

 

[alfredo]

Could it be my crap pod filters?

 

[Samuraiace]

Have you rejetted for your pod filters?

 

[alfredo]

Have you rejetted for your pod filters?

No. Had them rebuilt by a reliable forum member though with the right specs given.

 

[alfredo]

Curious to know what you guys are pulling in 5th gear at around 4k? Also, what is your cruising RPMs in 5th?

 

[pamcopete]

alfredo,

Here is a little Excel spreadsheet that will give you the RPM's vs MPH for all combinatins of gears, sprockets and wheel size:

RPM vs MPH

 

[bloodthirstysystem]

if you have cheap pod filters (like i do) they can cover the air passages at the opening to the carb. look where the air holes are and cut away the rubber on the filters. it also helps to not push them on all the way - put them on just enough to get a good clamp

and even if someone jetted them, you can only set the air mix screws while the bike is running.

 

[XSLeo]

Every bike responds to jetting differently. So even a pro can only get so close with the carbs in his shop. You need to read the carb guide and follow the jetting instructions there. Only on the bike testing can get them right.
On my 75 as a 650 it would pull 85+ all day long packed up with weeks of camping gear.
As a 750 it just does it easier and without so much vibes.
The stock 650 gets a noticable jump in power at 4-4500 rpms. This jump in power is accompanied by a matching increase in the vibes.
Proper tuning of ignition and carbs will smooth out the vibes.
With 17/30 130-16 tire I get about 65 mph at 4000 rpm. The 17/32 will get 65 mph at about 4500 rpm. The stock 17/34 is 65 at 5000 rpm.
From what I have found you get about a 100 rpm drop for each tooth smaller on the rear at 55 mph.
Leo

 

[alfredo]

alfredo,

Here is a little Excel spreadsheet that will give you the RPM's vs MPH for all combinatins of gears, sprockets and wheel size:

RPM vs MPH

Thanks Pete!

 

[pamcopete]

alfredo,

Here is a list of potential problems that can limit your top speed:

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 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
34. Weak TCI magnet in rotor. Unplug Reg/Rect to test

 

[pa23driver]

had the same problem as you - bike rattling and feeling like it was gonna blow up. sync'd the carbs and she runs so much smoother.

also, recheck your motor mounts. after i reinstalled the engine in the frame my motor mounts had a habit of rattling loose, and i could always tell if they were getting loose as the bike would start rattling pretty bad.

oh and sync the carbs

 

[ReycleBill]

Ran the bike around town and it seems like she doesn't want to do any more than 4k or 65mph. I haven't tried to go more, but it gets really loud and starts to vibrate more than seemingly normal. Now, I don't necessarily want to do more than 60/65, but some speed limits are 70 where I am and I don't want to feel like I am going to blow the motor, just trying to do the rate of traffic.

It shifts perfectly, doesn't slip, starts and runs just fine. This is all after a fresh rebuild with 3rd oversize.

I am 6'6" and 230lbs. Could it just be me causing it to seem like it shouldn't go any faster?

4000 @ 65 sounds about right for stock gearing and standard tire sizes. No two tachs or speedometers are exact but you're in the ballpark.

Like others have mentioned, tuning, carb sync, motor mounts and exhaust can make things seem a lot worse than they are. If vibration in the bars is a problem then I highly recommend a bar snake.

I re-geared to 18-34, weigh 220lbs and have hard saddlebags that are usually full of tools and crap and have no problem with 70-80 mile per hour cursing. I have pods but relatively quiet pipes. Re jetted one size bigger. Top end is somewhere above 110 (haven't found it yet) but I wouldn't want to stay there long. My Rifle Superbike Fairing helps but is too short for you as I'm only 5'-8" and wish the fairing was 2" taller.

After riding Hogs for years my first trip down the Interstate had me rethinking this bike but now that I've got it sorted out I'm really happy. Keep tuning and it will get better.

 

[5twins]

Cheap pods can cause problems right around 4K if they're blocking the air jets. Take them off and do a test run to find out.

 

[alfredo]

Just wanted to jump back to this and say thanks to everyone who threw in some help. Turned out it was a combination of out of sync carbs and shit pod filters. Took them off, sync'd the carbs with a manometer and cruised up to 6k with no issue. I must say that the vibrations are still there, but less than before.

 

[WacoBrian]

thats what i thought it was, GREAT job, and yeah it does vibrate more than any other bike i have rode

 

[Underdog]

in the xs 650 motor the pistons move together causing the vibration your still feeling