[Wishbone]

there is no in line filter between there and the carbs?

[97BladeRider]

Nope. It goes straight from the petcock to the carbs. No filter.

[Degsy]

There is a filter (strainer) in the top of the petcock assembly, inside the gas tank.

The petcock has a vacuum hose that goes to it and when the carbs are running, the vacuum pulls a spring-loaded diaphragm to one side to allow fuel flow.

It's possible I suppose that at those RPMs the vacuum isn't enough to pull the diaphragm because it has some crap in there that makes the diaphragm stick a little.

I'm dying for you to find out what the hell this problem is. I'm wondering if the new fuels are damaging the rubber inside the petcocks and vacuum pumps. I have seen 3 of these type issues in the past month now. Every one on a carburetter bike with a petcock.

derek

Derek

[97BladeRider]

Originally Posted by Degsy

There is a filter (strainer) in the top of the petcock assembly, inside the gas tank.

The petcock has a vacuum hose that goes to it and when the carbs are running, the vacuum pulls a spring-loaded diaphragm to one side to allow fuel flow.

It's possible I suppose that at those RPMs the vacuum isn't enough to pull the diaphragm because it has some crap in there that makes the diaphragm stick a little.

I'm dying for you to find out what the hell this problem is. I'm wondering if the new fuels are damaging the rubber inside the petcocks and vacuum pumps. I have seen 3 of these type issues in the past month now. Every one on a carburetter bike with a petcock.

Well, I pulled apart the petcock last weekend and it's fine. I did order a new diaphragm assembly and filter screen, because the screen looked like it was being twisted and sucked in toward the petcock's tube. Probably age and it's only plastic that's been sitting in gas for over 10 years. The diaphragm I'm replacing just in case. $43, shipped for the screen o-ring and diaphragm assembly, so it's not a huge expense.

The rest of the petcock is metal, either aluminum or steel, so I doubt there's any breakdown.

I'm anxious to solve this mystery as well. I want to ride!

[Stoneman]

Stator my friend. Stator...

[benVFR]

Originally Posted by Degsy

I'm dying for you to find out what the hell this problem is. I'm wondering if the new fuels are damaging the rubber inside the petcocks and vacuum pumps. I have seen 3 of these type issues in the past month now. Every one on a carburetter bike with a petcock.

derek

Derek

You thinking the E10 fuel blends are causing this?

There were warnings about it.

[TLRMan]

Sometimes it does go after the brass bits, and may attack the rubber stuff, but I've seen this problem with petcocks since the start of using vacuum to open them, so this isn't a new problem to me.

I know what causes the 3-4k bogs and usually it's a quick fix.....if it's petcock related, I know how to test that one out too.
If you brought the damn thing over to my place you'd be running good by now...
...and I can check the fuggin stator too.

[97BladeRider]

Originally Posted by TLRMan

Sometimes it does go after the brass bits, and may attack the rubber stuff, but I've seen this problem with petcocks since the start of using vacuum to open them, so this isn't a new problem to me.

I know what causes the 3-4k bogs and usually it's a quick fix.....if it's petcock related, I know how to test that one out too.
If you brought the damn thing over to my place you'd be running good by now...
...and I can check the fuggin stator too.

Well, if the new screen and petcock diaphragm don't do the trick, I just might take you up on this.

Damn stator is $250 new.

[jamotech741]

Ive never been a carb guy, but I do have limited experience with carbs. It sound like a flat spot that is "usually" fuel related. However I am familiar with cbrs and their stator problems, but "usually" it is also having problems with dying batteries if its a stator. If its not the stator which is easy to check, Id say its a fuel issue. Most likely not an ignition problem unless the stator is acting up causing voltage problems that can affect the igntion system. Paul D and tlrman are leading you on the correct path to diagnosis. Good Luck!

[97BladeRider]

Thanks. I'm still waiting on the filter screen and petcock diaphragm.

As far as the charging system goes, the battery seems to be fine. The bike hasn't died while running.