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High performance pipes

  • Thread starter Thread starter Craig
  • Start date Start date
C

Craig

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I am still having problems with the V&H 4-1 pipes on my 1100. The tuner can't get rid of the flat spot in the mid range. He feels that it is the pipe and no amount of carb work will help. Any other suggestions out there for a "better" pipe?

Craig
 
Dynojet kits are available. They typically come with a drill bit to open up the vent hole to the CV diaphragm - allows the slide to lift more quickly thus eliminating a flat spot. Not sure this is the answer per say, but it may be the answer. Lots of people use V&H pipes and don't have this problem.
 
Sorry...I should have told more info. 1166cc kit. Higher lift- longer duration cams. Cam sprockets at approx 108 and 109 degrees. Mikuni 36mm smoothbore flatslides + pods. Dyna ignition. It has been on the dyno and we cannot get rid of the flat spot in the mid range. We feel it is the pipes. Any ideas.
 
CHEFF...where are ya on this one? [-o<
KEITH... ya out there? [-o<

Too many goodies / mods for my advice on a Suzuki. Now if we were talking small or big blocks...I could give you some sound advice. :?
 
I would think carbs, not pipe. I had 1148 kit, mild cams, & 36mm cv's from an 1150, degreed from 104 to 112, with both Yosh & V&H pipes. With carbs right, no sign of flat spot anywhere.
 
What throttle postition is the flat spot occurring.
How many miles are on the 1166.
Compression numbers?

You have a great set up and should be rockin and a rollin right now. I don't think it's the pipe. I've seen many V&H pipes tuned right.
 
its almost certainly the carbs presuming everything else is in good order

my advice is find a better dyno man :-D
 
The flat spot seems to be from 1/4 - 3/4 throttle. The last 1/4 is so low due to the mid range being so crappy...only 75 HP max!!. I had a set of MAC 4-2 and it was running pretty good. It topped out at only 104hp. We figured that it was the pipes limiting the HP, so I went to the 4-1 V&H.

Craig
 
Read the plugs by doing a plug chop and set the needle jet by raising (richen) or lowering (lean).
 
yes, we have moved up and down on the needle..as well as different mains.

Craig
 
or perhaps a different sized pilot jet? seems to be in the low end of midrange isnt that where the pilot begins to mix with the main?
 
Where do you have the acc pump set?

120 or 125 mains?

are you using an A/F meter and if so where is it at from 7000rpm up?
 
I will have to check with my tuner to get more info. I will see if he can jump into this thread.

Craig
 
That range is right where the accelerator pumps do their thing. You can try pulling the pump rod out and run without the pumps so you can get the jetting right then reinstall the rod to get the pumps working again. When you first nail it with smoothbores you have to roll the throttle on rather than just whacking it open. They'll bog the engine if you don't have enough rpm's spinning and you just yank them open. Once you get it up to redline after whatever gear you were in you can just yank the throttle open after shifting, but you have to regulate the throttle a little and downshift when you first nail it.
 
One thing I'd take a close look at is float height considering where your flat spot is.
 
One thing I read once was that some 4 into one pipes have a
flat spot that a 4 into 2 into one pipe does not have.
Could that be what the tuner is referring to?
In the picture, you have to look closely because
the exhaust does end up on one side with both
systems but supposedly there is is difference.
Don't see how it could make that big a difference
.........
 
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