Bike won’t rev past 4-5k rpm

[TrickyTriggs]

My 1996 GS500E was working fine then one night the bike lost a lot of power and wouldn’t rev past 4-5k rpms. As well as severe engine deceleration. I noticed also that the bike had some rattling noise that increased as the engine increased. I figured it was a carb problem so I cleaned the carbs, problem still persisted. Replaced the spark plugs, still no luck. Synced the carbs, bike ran great at idle but had a bad time revving up. Figured I fixed it after the carb clean, I went for a ride but the problem still persisted; on my way back the bike shut down completely as if fuel starved. One thing to point out is that the extreme engine deceleration pull at 4-5k rpms did not feel like a fuel starvation but rather like something was preventing the engine from running. Any ideas?

[JohnnyBravo]

TrickyTriggs! Glad to have you aboard...

[DannoXYZ]

Hi and welcome!

Carbs never make that kind of noise, maybe some hissing if you've got a vacuum-leak; no big moving parts inside.

• How many miles on bike?
• Last time cam-chain tension was adjusted?
• Last time valve-clearance inspected and adjusted?

That "rattling noise" you mentioned sounds like loose cam-chain.

[TrickyTriggs]

20100 miles on it, recently adjusted the cam chain, inspected valve clearance 2 days ago, all within spec. One thing to note when if first went to **** it lost a quart of oil without me knowing it.

[TrickyTriggs]

Also the left carb diaphragm was initially wrinkled but it ran fine and there weren’t any holes.

[Abu_Mishary]

Be more specific on "wouldn’t rev past 4-5k rpms". Will the engine dead when pass 5K?

[TrickyTriggs]

It would rev to like 4-5k rpm, and when you role the throttle even more there’s no effect.

[TrickyTriggs]

The revs just stay the same until they slowly reduce because of the execive deceleration and vibration of the engine. Thinks I know I can rule out:
- wheels
- chain (minimal surface rust but I keep it lubricated)
- chain guards (normal wear)
- battery/stator (bike runs at full electrical power when turned on)
- throttle cables (full range of motion with snap back)
- fuel (previously had water so I replaced it with new fuel)
- choke Cable (works like it’s supposed to)
- oil (lost a quart so I added it back, problem persisted)
- valve clearance adjustment (within spec)
- spark plugs (replaced)
- Fuel lines (replaced)
- tank fuel filter is clean
- Petcock (Works properly)
- Carburetor (completely cleaned but problem came back)
- ~>float height is correct
- ~>New gaskets and o rings
- ~>New float needle and seat
- ~>diaphragms are good
- ~>needles are good
- ~>Nice and tight seal between Airbox->Carbs->Engine
POSSIBLE CAUSES (?) signifies “I’m not sure”
- fuel delivery
- electrical?
- ~>CDI unit?
- ~>ignition Coils?
- ~>Other electrical parts?
- Engine (rebuilt a couple of weeks ago, got rid of carbon deposits.)(replaced all gasket)
- ~>Worn piston rings?
- ~>Worn piston rods?
- ~>Gearbox?
- ~>Clutch?
- ~>Broken Valve?
- ~>incorrect oil pressure?
- ~>oil filter?
- ~>other broken engine parts?

I appreciate the help, please any input would be fantastic. Obviously I know a thing or two about repairing bikes, which doesn’t mean I’m perfect. So if you can look over my findings so far and maybe see something I missed that would be great. My car is going to **** and winters coming so I want to refrain from driving my car as much as possible so I can make it through winter. I would like to get my baby back to health ASAP.

[DannoXYZ]

Can it rev past 4.5k neutral, just engine by itself?
What happens if you remove airbox?

[TrickyTriggs]

You know I was thinking of that, I was going to remove so I could make sure the carbs worked properly. I will do that Wednesday. But keep in mind it idles great.

[TrickyTriggs]

Water in fuel sounds like a prime suspect so I’ll perform the test and I’ll get back to you, keep brainstorming it’s great information

[DannoXYZ]

While you have airbox out, take a look and see if slides are opening properly when revving. If they're stuck halfway, that may explain the 4.5k-RPM limit.

[TrickyTriggs]

https://m.youtube.com/watch?v=ScatQF-SzUo The symptoms are much like what’s in this video.

[DannoXYZ]

Sure, wouldn't hurt to drain your tank and float-bowls, then start with fresh gas.

[TrickyTriggs]

Yeah lol that was my plan to check out the slide functionality. And yeah it revel to like 8k rpm in neutral. I just checked on it and it wouldn’t even start, which would make sense if there’s water in the fuel because all the water would settle in the float bowls.

[Triple Jim]

The bike in the video is losing one cylinder intermittently, you can hear it.

Did you actually run the engine for any length of time while it was a quart low on oil? That's awfully low.

[TrickyTriggs]

https://m.youtube.com/watch?v=zdYA1T2Llkw
This actually me and my bike, you can here the noise, what do you think it is?

[jkv45]

Originally Posted by TrickyTriggs

https://m.youtube.com/watch?v=zdYA1T2Llkw
This actually me and my bike, you can here the noise, what do you think it is?

That reminds me of another video of a Ninja 250 making odd sounds. Turns out it was significant internal engine damage.

Have you drained the oil and looked for any signs of damage?

Other things that could make noise would be a weak can chain tensioner or an issue with the valves.

A not-so-obvious carb issue could cause the rev problem. Check that the slides rise and fall smoothly. I know you said the diaphragms were ok, but that is something else that might cause the rev problem.

Always start with a clean/empty tank and known good gas.

I'll see if I can find the thread.

EDIT: This isn't the exact one I was looking for , but some similar symptoms - https://www.ninjette.org/forums/showthread.php?t=305325

This might be it - https://www.ninjette.org/forums/showthread.php?t=305723 - but it doesn't look like there is any resolution. I might have been mixing-up the two.

[TrickyTriggs]

It sounds like a valve or cam tensioner from the location of the sound in the top end. I’ll check the oil for metal as well.

[Triple Jim]

Of course it's best to check the easy to fix stuff first, but with the quart low thing, my bet is on internal engine damage. That engine and transmission hold only about 2 quarts.

[TrickyTriggs]

Correction; engine holds 3.5 quarts of oil

[Triple Jim]

I see that various sources seem to have different specs, but the GS500/F owner's manual says 2.7 quarts without the filter. Not to argue about trivia, but you did mention that the problems started at the same time you found the oil a quart low. I'm not clear on the exact sequence of bad running and finding low oil though.

Keep in mind that I'm rooting for you to find a simple problem that's easy to fix.

[TrickyTriggs]

I always put 3.5 quartz in, anyways, I took off the airbox and here’s what happened:
https://m.youtube.com/watch?v=QCTRtfy8vw0

[Triple Jim]

I don't see anything unusual there, other than the engine is having trouble idling.

[TrickyTriggs]

That’s because the bike is running lean since I took the airbox out; I had to use the choke to riches the mix. Full choke it revs to like 2100 rpm

[jkv45]

The carbs need to be gone through, cleaned, checked, and adjusted.

That does look odd to me. Damaged diaphragms seem like a good possibility, but there are internal carb issues that could cause that as well. Dirty jets or restricted passages can do it.

It should still run and idle halfway decent (when warm without the choke) with the airbox off - if everything else is right.

I would still double-check the valve adjustments and confirm the can chain is snug.

Do we want to move this to the Tech Section?

[TrickyTriggs]

I just talked with a friend who worked on bikes as well and he said that it was either my cam chain or the tensioner. How to I know if they need to be replaced?

[DannoXYZ]

Originally Posted by TrickyTriggs

I just talked with a friend who worked on bikes as well and he said that it was either my cam chain or the tensioner. How to I know if they need to be replaced?

The noise and trouble starting after running low on oil points towards a mechanical issue with engine. Get FSM and do the following in order:

- lock & load tensioner, manually spin engine around a couple times to verify tension correct
- check cam-sprocket alignment and cam-timing
- check and adjust valve-clearances as needed.

There are marks on the cam & sprocket that you'll want to make sure is aligned properly.

As previously mentioned, check your oil for metal particles. Cut open filter and inspect what it's trapped.

[TrickyTriggs]

Ok so I went and checked out the cam chain. I tightened it as much as I could then moved the crankshaft. It slightly released pressure on the cam chain tightness. I also noticed that there was an air leak in the left vacuum tube where you go to sync the carbs. I’m guessing that it makes a difference. Which explains why the left spark plug was significantly whiter than the right one. So if there’s a slight decrease in pressure in the cam chain, does that mean I have to replace the tensioner?

[TrickyTriggs]

I will check the alignment later tonight, as well as the cam timing.

[TrickyTriggs]

Also one thing to point out; it has a cut-off exhaust.

[TrickyTriggs]

Cam timing looks correct I’m not sure how to check the alignment. The two notches are point inwards as the same time the rt mark is aligned.

[jkv45]

Is the cam chain taught?

Double check the valve clearances while you are in there.

[TrickyTriggs]

Originally Posted by Triple Jim

The bike in the video is losing one cylinder intermittently, you can hear it.

Did you actually run the engine for any length of time while it was a quart low on oil? That's awfully low.

I actually don’t know. I was riding the bike for a while until I checked that the oil was gone. So it could be one ride, or it could be many. I’m not sure.

[jkv45]

Originally Posted by TrickyTriggs

I actually don’t know. I was riding the bike for a while until I checked that the oil was gone. So it could be one ride, or it could be many. I’m not sure.

Now you know - the Ninja will use some oil.

It gets pumped into the airbox from the crankcase breather during high RPM running, so it's something that needs constant attention.

[Triple Jim]

Originally Posted by jkv45

Now you know - the Ninja will use some oil.

Except this is a 1996 Suzuki GS500E.

[TrickyTriggs]

Ok so I went back to the bike today and I cleaned the carbs and then ran it. Still ran bad. So I took it back and then I did a spark plug test and I noticed that the rattling noise only came from the left side which is the same as the video above.

The left spark plug ran rough and barely idled, where as the right one idled fine. Could the cause of this be a bad ignition coil on the left side?

[Triple Jim]

You can find out by swapping the coils.

[Alex]

/moved to General (with forwarding link remaining)

[DannoXYZ]

Check the oil & filter for metal fragments.
Pull the left rod-cap and measure bearing clearance...