Gs650e carb tuning for mac 4-1 and velocity stacks

[boris.h]

I will try 1.50mm to start, so 1.50mm is about DJ# 140.. I have the same configurationthan you, velocity stacks, bandit header whitout any muffler for the instant
How is your idle? Did you screw the idle screw a lot to get a good idle? Mine is almost completely unscrewed to have a 900 rpm idle...

[boris.h]

ok, lot of hesitation again, and the engine heats a lot. White plugs when cruising and accelerating. Going to drill my jets to 1.65mm --> DJ152 mains.... will test it by the end of the week

[ddlaz]

Not much helpful advice in this thread yet, so I'll try to help. I have the same engine, at least the same top end and carburetors on my 550, and I also cannot use a stock airbox. The 550 airbox won't fit the CV carbs which are positioned farther back than they are on the 550 head, and the 650 airbox won't fit in the 550 frame at all. I have K&N pods, the double ones since the singles also don't fit, a Kerker pipe and a Dynojet kit, haven't had the time to get it tweaked to perfection yet.

Can you please start with as detailed a description as you can about the problem? I read the first post a few times, not quite getting it. Is it only RPM related? Throttle positon related? Only happen in fifth gear?

Just a quick thought, if those jetting changes you have done have no effect, maybe it's the ignition?

The problem is hesitation or surging or bogging, however you want to call it, while cruising in 5th gear on the highway around 5700 rpm. It's not at a specific frequency but it will continue bogging then clear then bog then clear constantly until I change throttle positions to either speed up or slow down.
It is more prominent in 5th but that's because I don't do much cruising at 5700 unless I'm on the highway.
Yes I did mention in my post that I'm thinking it's an ignition issue.
Since my OP I've checked the timing and the advancing is working properly as it will advance to 40 degrees but there is an intermittent flicker that throws off the timing. Not sure how to explain it other than its not a constant timing light flash.

[mmattockx]

The problem is hesitation or surging or bogging, however you want to call it, while cruising in 5th gear on the highway around 5700 rpm. It's not at a specific frequency but it will continue bogging then clear then bog then clear constantly until I change throttle positions to either speed up or slow down.

As tom203 mentioned, CV carbs need some intake vacuum to operate well. This may be vacuum related and something that simply can't be cleared while running the velocity stacks. Does 5700rpm equate to a speed you run regularly? If you really want to keep the stacks would changing gearing a tooth or two on the back solve your issue? Is it possible to try longer velocity (or shorter) stacks to see if that changes your issue? How does it run if you remove the stacks altogether?


Mark

[JJ]

Velocity stacks belong on the race track, or in the garbage, NOT on the street...

[ddlaz]

As tom203 mentioned, CV carbs need some intake vacuum to operate well. This may be vacuum related and something that simply can't be cleared while running the velocity stacks. Does 5700rpm equate to a speed you run regularly? If you really want to keep the stacks would changing gearing a tooth or two on the back solve your issue? Is it possible to try longer velocity (or shorter) stacks to see if that changes your issue? How does it run if you remove the stacks altogether?


Mark

Thanks for your reply. 5700 isn't my usual cruise rpm but my friends cruise around this rpm so it usually just rears it's ugly head when I'm with them. Otherwise it doesn't bother me... More like an unsolved mystery type deal.

I took stacks off and still had the same issue. I understand that CV's need vacuum to operate well but I read of a few people running pods and jet kit without issue. Figured I'd follow up.

[mmattockx]

I understand that CV's need vacuum to operate well but I read of a few people running pods and jet kit without issue.

I have APE pods and a Kerker 4-1 on my 1100E and it runs fine, but velocity stacks offer zero vacuum where the pods seem to offer just enough to keep the CV's happy.


Mark

[ddlaz]

I have APE pods and a Kerker 4-1 on my 1100E and it runs fine, but velocity stacks offer zero vacuum where the pods seem to offer just enough to keep the CV's happy.


Mark

Definitely some merit to this! Put on some dual pod filters last weekend, no more cruising bog. Thanks for the suggestions!

[JonnyC]

Well damn. Velocity stacks will be arriving soon to replace my K&N dual pod filters. I just wanted to give them a shot, but it looks like it will make things worse.

[ddlaz]

Lol...well if you tune it just right, itll be a subtle bog at cruise only. Something i couldnt live with.

[JJ]

Velocity stacks aren't for the street. Off-road only...

[ddlaz]

Amen. BUT...I can't see this bike working well with these stacks at all. I had an issue at both ends of the lean and rich spectrum.