Help, My girl lost her top

[tothemax93]

I was at the drags tonight. While I was doing my burnout, it sounded like it was overrevving(floating out) but the rpms weren't that highmaybe 5 0r 6 thousand. I proceded to do a dry run and it didn't feel just right. So I go down the track, and the bike feels really weak. I had made 3 passes before this one and everything seemed fine. Now every bad thing that could happen is going through my mind. So at this point I'm trying different things to see just how it's acting. My conclusion is that it runs perfectly normal until i get to about 4000 rpm's. Then it acts like I have a rev limiter. It will go higher, but It's extremely choppy and ruff,and that is in any gear wether I go up slowly, or get after it. My girl lost her top end.I drove it home without issue, and as long as I stayed under 4 grand every seemed normal. What should my next step be in diagnosing this. I haven't looked at it mechanically at all yet. Any idea's on where to look first.
Tim

 

[gamorg02]

make sure the carbs are seated and no air leaks, lot sof guys have similar issues if their airbox is off. just a starting point?

 

[tothemax93]

Thanks Garrett, that will be the first place I look.

 

[gamorg02]

maybe a crack appeared somwehere? i dunno. just a guess at this point. does anything 'sound' off?

 

[Rollie]

Fuel filter is quick & easy to check.

 

[jfeagins]

Fuel pump diaphrams may BOTH be out of place and causing poor fuel pressure - wouldn't sustain top RPM's ???

When you turn on the key, does the pump go crazy trying to build initial pressure?

 

[95spfldmax]

make sure the carbs are seated and no air leaks, lot sof guys have similar issues if their airbox is off. just a starting point?

Spray some WD40 around engine & airbox. Listen for idle change.

 

[gamorg02]

i've found starter fluid finds leaks faster/better. i believe danny uses propane

 

[tugla]

i've found starter fluid finds leaks faster/better. i believe danny uses propane

is that why he always shouts FIRE IN THE HOLE!!!!!!!!!!!!!!!!!! :rofl_200::rofl_200: flash backs or something :ummm: unk:

 

[tothemax93]

i've found starter fluid finds leaks faster/better. i believe danny uses propane

I prefer Acetylene myself, but I'm out of it right now. I just got home from work so I'm going out now to take a look. Thanks for the advice.
Tim

 

[4gasem]

Another option may be the tank isn't venting properly and is building pressure.

Chris

 

[tothemax93]

I took a bit of a look at it tonight. I pulled the air box to make sure everything was tight, I sprayed wd 40 around the carb boots. nothing changed. I pulled the fuel filter, blew it out. It seemed pretty clean. I ran it for a few minutes then pulled the plugs out. three were perfect and the front right had good color like it had been running good, but it was a little wet. Maybe just a bad spark plug.. I went for a ride after I did all the stuff, and it acted the same. Good up to 4 grand then miss after that. I'm going to get new plugs for it, and dump some seafoam in it, and see if that gets me anywhere. I'll chech the vent lines on the fuel tank also. Does anyone have an opinion on a possible electrical problem. A couple people I talked with mentioned a possible CDI Issue. Thanks again for the replies.
Tim

 

[gamorg02]

check the carb vents too.

 

[tothemax93]

Problem solved. Anybody care to harbor a guess as to what fixed the trouble. I'll give you a clue. There are a few threads on the forum about this wonderful, magical, all curing, life changing liquid. Lets all say it together """""""unk:

 

[gamorg02]

seaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaafoam

 

[tothemax93]

Give that man a prize. I started out yesterday by putting new plugs in and 6 oz of seafoam in the tank. I rode for about 20 miles, and it was running as ruff as before. I did notice a different smell at one point in the exhaust, like a piece of gunk went through, but it still was running poorly. I went to my sons lacrosse game with it, and after the game I was riding home and it was completely back to normal. It's funny how in your mind, you go from a complete motor tear down, and it's really just piece of dirt in the carb.Tim

 

[tothemax93]

I may have spoken to soon. This same problem has been occuring, hit and miss since my last post. I've raced several times and have been in the 7.6 range but then a few runs later it will in the mid 8's and feel very weak. I did the pea shooter today, but we have rain so I didn't really get a chance to run it good. I'll try the shotgun next if the pea shooter doesn't work. Just to refresh, the bike feels normal up to 4 grand and then has a miss after that, and falls on its face. Any other thoughts on the problem, anything electrical maybe.:confused2:
Tim

 

[tothemax93]

I have another clue to the issue. I pulled the spark plugs today. The left side ones were perfect. The right side plugs had some black and not as clean as the left side. So it seems the problem is occuring on the right side. Both the right side plugs were the same.Is there something on the vmax, whether it be fuel or spark, that works on a right or left side basis.:ummm:

 

[one2dmax]

carb sync effects right and left side.

 

[tothemax93]

A little update:
I did the shotgun last weekend. The A/F screws had a little rust on them, and there was some visible dirt. After we were done with the shot gun, I decided to take it for a ride before we synced the carbs to really determine if dirty carbs was the problem. I went easy at first. Ran the RPM's up easy, and I didn't have the miss above 4000 rpms. When the bike was running good before, when I shifted from 1 to 2nd the front end would come up, and that was the gauge to see if was back to normal. So I get right on it, and when I shifted from 1st to 2nd the bike winds up super quick and the front end shakes. At first I thought I missed 2nd, but then realized the tire broke loose. After I got the grin off my face, I went back and synced the carbs, and all is well. The beast is even more powerful than I thoughtunk:
So my suggestion to all you guys who are having problems with your bike running poorly above 3500-5000 RPM, start with the shotgun. I would have sworn it was electrical, but I was wrong as could be.
Tim