BIG THANKS to Dragmaxster! Still need some help

[TB99Max]

So this might be a long one........ I've been chasing down this issue since I bought the bike ( June of 2015 ). Thought it ran decent but anytime I tried to hold a consistent speed anywhere from 50MPH-75MPH it acts like its running out of fuel. So with the help of everyone on here I checked the fuel pump, changed the fuel filter, did the peashooter, did the shotgun and nothing changed. So John (dragmaxster) offered to rebuild my carbs and he actually drove over 80 miles to my place and took them off! I offered to take them to him but he said don't worry about it!! SUPER COOL! So carbs got redone and he delivered them AND synced them for me. Bike ran better everywhere but still had that pesky stumble...... FRUSTRATING!! So talked to John about it and he told me to check the coils, he sent me some on his dime to use and still had the same problem. Next step..... he made me some COP'S and still the same issue! So I'm looking for some suggestions for what I should check next??
And like the title says I want to thank John for all his help! It's very rare these days to find a stranger that will help you out like he helped me!

 

[TB99Max]

Also, the V-boost is disconnected so its on or open all the time.

 

[wildweasel_pt]

Kudos on him for that. Does that stumble happens either with bike cold or warmed up? From the top of my head I would go for pickup or TCI next (check resistance on the pickup - see service manual). The stumble is according to speed or RPM? Speed doesn't make much sense. Its possible that TCI fails in a specific rpm range but if that is the case you should get exhaust banging due to unburnt fuel on cylinder. Did you actually stripped the fuel pump to check condition of the inner parts? You may also have a defective diaphragm not coping with the fuel demand from carbs and engine stumbling due starvation.

 

[Hellboy]

Maybe plug the V-boost in and unplug it in the closed position to see if it still does it? If it changes it might mean that it is a fuel thing, if not, then electronic I would think. Also, you stated 50- 75. What about 80+? does it actually get better or have you tried?

Matt

 

[jfeagins]

Did anyone take note of your carb internals while they were off? All stock jetting perhaps, mixed with aftermarket pipes maybe? Or has the jetting been changed, and a kit put in like a stage 7 jet kit? Lots of things can make this surging symptom.

 

[Dragmaxster]

Did anyone take note of your carb internals while they were off? All stock jetting perhaps, mixed with aftermarket pipes maybe? Or has the jetting been changed, and a kit put in like a stage 7 jet kit? Lots of things can make this surging symptom.

Stage 1 kit, dj160 jets, slides not drilled, needles were on 3 clip from blunt, aftermarket carbo fiber slip-on, A/F mixtures were all over the place, 1 1/2-3 1/2-4 1/2 and 6 turns out--i had him send a pic of the plugs first and dropped the needles to the 1st clip.
I put them on my bike to test them and get the sync close and mine never ran that good.
I suggested smaller mains at his altitude but i believe it's electrical too. TCI is what i thought and i offered to put mine on and troubleshoot taking one part at a time off of my bike.

 

[lethal dose]

Are the carb vent lines on? If not, I'll bet this is your issue.

 

[TB99Max]

Are the carb vent lines on? If not, I'll bet this is your issue.

You are talking about the vent lines/ overflow lines that come off the tops of the carbs right?

 

[TB99Max]

Kudos on him for that. Does that stumble happens either with bike cold or warmed up? From the top of my head I would go for pickup or TCI next (check resistance on the pickup - see service manual). The stumble is according to speed or RPM? Speed doesn't make much sense. Its possible that TCI fails in a specific rpm range but if that is the case you should get exhaust banging due to unburnt fuel on cylinder. Did you actually stripped the fuel pump to check condition of the inner parts? You may also have a defective diaphragm not coping with the fuel demand from carbs and engine stumbling due starvation.

I would say its speed related. Weird thing is, if I get on the throttle hard it doesn't happen. Only happens if I try to hold a consistent speed or accelerating kind of easy, but when it does happen if I give it a good amount of throttle it takes a second or two but then it will accelerate out of it.

 

[TB99Max]

Maybe plug the V-boost in and unplug it in the closed position to see if it still does it? If it changes it might mean that it is a fuel thing, if not, then electronic I would think. Also, you stated 50- 75. What about 80+? does it actually get better or have you tried?

Matt

I had the v-boost plugged in like normal and it does it. Unplugged the v-boost in the open position and the bike does feel faster but it still does it. Above 80MPH it does it but it doesn't seem as bad. I'm thinking that it doesn't feel as bad because the RPM's are higher and if I get on it hard it comes out of it a little faster.

 

[davesax36]

Are the carb vent lines on? If not, I'll bet this is your issue.

Why?

 

[Dragmaxster]

Why?

If one of them gets kinked or pinched between the airbox and frame it will cause a disruption in the float bowl, but just left off won't hurt it.
The fuel pump ran normal without running unusually long-Not sure which diaphram WW is refering to but all 4 in the carbs were very good with no holes or tears- there are 2 in the fuel pump that will flip out of place but then the pump will continually run. The fuel pump is easy to take apart and rebuild though.
I think we left the 4 vent hoses off didn't we Tim?

 

[TB99Max]

If one of them gets kinked or pinched between the airbox and frame it will cause a disruption in the float bowl, but just left off won't hurt it.
The fuel pump ran normal without running unusually long-Not sure which diaphram WW is refering to but all 4 in the carbs were very good with no holes or tears- there are 2 in the fuel pump that will flip out of place but then the pump will continually run. The fuel pump is easy to take apart and rebuild though.
I think we left the 4 vent hoses off didn't we Tim?

Yeah John no vent hoses. I think I'm just gonna have to learn to deal with it!

 

[Dragmaxster]

I think WW is probably right with the TCI box.

 

[lethal dose]

The hoses being left off WILL AFFECT IT. I chased my tail for two months trying to figure out a high speed surge... once I put the hoses on, it went away. Try it. Trust me.

 

[davesax36]

That sucks. I have no idea where mine are. I'll figure something out.

 

[TB99Max]

The hoses being left off WILL AFFECT IT. I chased my tail for two months trying to figure out a high speed surge... once I put the hoses on, it went away. Try it. Trust me.

At this point I might as well give it a try..... Why not right? Cheap, quick, and easy to do! I won't be able to get to it until Wednesday afternoon but I will definetly post an update when I do.

 

[lethal dose]

Copy that.

 

[Dragmaxster]

Well i hope it does work for you but i've never had them on and it has never affected mine. I just sold them to another member here.

 

[Traumahawk]

Well thats why Seans kit....vs the stage 7, still has them. There has been talk of this before on the VMOA group.