My motor seems broken after I overrev'd

VMAX  Forum

Help Support VMAX Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

bkuberek

Well-Known Member
Joined
Jun 28, 2015
Messages
73
Reaction score
0
Location
Forest Hills, NY
It's a 1991 vmax and it's my first ever bike. I finally got comfortable with it and started exploring the vboost. I think I hit 11+ on the tach on first gear for a few seconds. The day after my engine sounds weird and has a clicking sound in front right cylinder. Once the bike warms up the sound improves enough that it is almost unnoticeable but I can't ride over 6rpm anymore. Once I hit 5 or 6 on the tach the bike starts to loose power.

What have I done to the bike? Is there any hope to get it back?

Thanks

Sent from my HTC6525LVW using Tapatalk
 
I think the big ends of the rods don't like to be over revved but can't remember. Sean is one of our motor experts, when he sees this he can respond to your post.
 
It's a 1991 vmax and it's my first ever bike. I finally got comfortable with it and started exploring the vboost. I think I hit 11+ on the tach on first gear for a few seconds. The day after my engine sounds weird and has a clicking sound in front right cylinder. Once the bike warms up the sound improves enough that it is almost unnoticeable but I can't ride over 6rpm anymore. Once I hit 5 or 6 on the tach the bike starts to loose power.

What have I done to the bike? Is there any hope to get it back?

Thanks

Sent from my HTC6525LVW using Tapatalk

Usually when overreving and engine the valves will "float".
Probably going to need readjusting.
 
Ok thanks. I will get a quote from the mechanic on that. I have recorded a video of my engine running. Is that something useful here?

Sent from my HTC6525LVW using Tapatalk
 
It looks like your carbs are not seated properly in the rubber boots and it sounds as if you have a air leak (more noticeable near end of video) which would support the carbs not being seat properly.
 
Ok here is a link to a video I just took. I tried to capture the sound as clearly as I could but it's not coming as it once did.

https://goo.gl/photos/PQQCjTA1tfeDMBh48



Sent from my HTC6525LVW using Tapatalk

At 2:04 sec on your video take the 2 screws holding that chrome boot cover and look at the carbs. By the look of the chrome brace(with the warning writing on it) holding the carbs together they are out of line and #1 carb is out of the
boot.
Looking again at the video and it just looks like #3 carb is out.
 
Last edited:
I think carbs are seated but it looks like the right rear intake might be broken where the chrome cover bolts on. If that's broken off it could have a vacuum leak causing some running issues.
 
I took the covers off and attached some pictures. Seems the cover on the right side had broken off and was welded on. Might be some kind of epoxy material. uploadfromtaptalk1440366171251.jpguploadfromtaptalk1440366185968.jpguploadfromtaptalk1440366237909.jpguploadfromtaptalk1440366248330.jpg

Sent from my HTC6525LVW using Tapatalk
 
If you look right there in pic #3, just to the left of the vacuum cap clamp, there appears to be a bit of a crack.
 
Right. I took a close-up now and it can be seen better.

So this is the source of the pop in the exhaust or the the reason the cylinder is failing? I might still have issues with the floats as well correct?

Thanks again for all the help. As you may notice I'm a novice.

uploadfromtaptalk1440368371332.jpguploadfromtaptalk1440368386074.jpg

Sent from my HTC6525LVW using Tapatalk
 
Right. I took a close-up now and it can be seen better.

So this is the source of the pop in the exhaust or the the reason the cylinder is failing? I might still have issues with the floats as well correct?

Thanks again for all the help. As you may notice I'm a novice.

View attachment 50478View attachment 50479

Sent from my HTC6525LVW using Tapatalk

I dont think its on the carb boots themselves, but the only way that you can truly tell is to take the carbs off, and look down inside of the carb boots. I was talking about cylinder#3, which is the right rear, right where the epoxy is (the epoxy is grey) but looks like a crack that is white....like it cracked, and a small piece of the epoxy fell off.
 
Got a few issues to look at and then a better resolution can be decided. I do have a set of good intakes to get rid of the JB welded ones. Also, I suggest replacing the carb boots (maybe all the rubber boots including the ones for the airbox if they aren't soft and supple too).

Not saying this is going to be the 100% fix but looks like maintenance that needs done. Might also need to replace the spark plugs.

Sean
 
I dont think its on the carb boots themselves, but the only way that you can truly tell is to take the carbs off, and look down inside of the carb boots. I was talking about cylinder#3, which is the right rear, right where the epoxy is (the epoxy is grey) but looks like a crack that is white....like it cracked, and a small piece of the epoxy fell off.
Looked carefully in that area and I don't see a Crack. The white lines are there from me scraping it earlier to see what kind of material it was. Seems to be a big chunk of epoxy and perhaps it covers a hole since there is so much of it.

Sent from my HTC6525LVW using Tapatalk
 
Got a few issues to look at and then a better resolution can be decided. I do have a set of good intakes to get rid of the JB welded ones. Also, I suggest replacing the carb boots (maybe all the rubber boots including the ones for the airbox if they aren't soft and supple too).

Not saying this is going to be the 100% fix but looks like maintenance that needs done. Might also need to replace the spark plugs.

Sean
How should we discuss about the intakes? I have an appointment with the mechanic this Tuesday for tires and fluids I am going to ask him for valve adjustments and new boots. Do you think I should put a new intake as well?

I have replaced the spark plugs just a couple of days ago. I got new NGK iridium plugs. Posting a picture of the old ones. uploadfromtaptalk1440384368564.jpguploadfromtaptalk1440384439894.jpg

Sent from my HTC6525LVW using Tapatalk
 
Here is another video from above with a different sound. Seems that the engine skips or hits something. You can hear it at 0'16" and 0'32" and later as well.

https://goo.gl/photos/89qbmmfcGpPJnMFi7

Sent from my HTC6525LVW using Tapatalk

Your plugs look ok-All of the intake carb boots are probably going to need replacing.I am pretty sure all 4 are going to be cracked. Can you post a close up of the intakes rubbers on the others side.
After seeing the photos and the video i now doubt you will need valve adjustment.
 
If you have the stock coils the iridiums are going to be gapped at 32.
If you have cops they should be gapped at 27.
BE CAREFUL if you have to gap them. The tips are known to break off as they are tiny and the insulators are very fragile.
Ok see your coils are stock.
 

Latest posts

Back
Top