Topica Loopframe_Guzzi Archive
 

Subject: RE: Exhaust & Carb Tuning

Author: halc-@comcast.net

Date: Jul 20, 2005, 10:19 AM

Post ID: 1719181891


The location of the x-over , if I remember, is better after the header pipes unless you are running large carbs.

Good Luck
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halc-@comcast.net wrote:
 Joe

After a quick peruse of your email I came up with general approach to
your problem.

Do the easiest thing first. Carbs. Is it gas starved at mid-range?
Move the needles up a notch.


I'm prety sure my needles are raised to max, but I should check
again, and while I'm at it I'll get all the present jetting data.


 
Though I believe it is a cross over issue. Going from memory, not alway
a good thing,
I remember my experiences with and w/o x-overs. Without the x-over
 there wasn't enough back pressure. I lost top end. With more
restricted cans w/o x-over the mid range was an issue.

So I put on a crossover and ran less restrictive cans (OEM dunstall
mufflers) That ended up giving me plenty
of UMPH throughout the RPM range. And a louder exhaust.


So maybe I'm onto something here. Seems that the H-pipe style x-over was
effective on the T-Bikes and continues to be popular with the late-model
injected Tonti tuners too. My previously described idea for a x-over is
basically an H-pipe, but will be located farther down stream than where
it's placed on the later machines and the early LeMans used a x-over up
close to the heads, as did Norton & BMW. Do you think location of the
x-over matters greatly? Also, do you think the diameter of the pipe that
crosses over is critical?


 I believe Guzziology has a write up about the effects of velocity stacks
and exhausts.


I failed to mention my air filters; K&Ns slipped over a set of stacks
that I believe came from a Convert, that have been turned down smooth to
slip into the filters. These stacks are about 2 1/2" - 3" long.

I also didn't mention my dist, which is the standard loopframe single
point unit. Recently I did replace the heavy loop-ended advance spring
with a second lighter spring as recommended by Mark in an effort to get
a linear advance curve more similar to that of a dual point dist. But
I'm pretty sure the advance is maxed out by 4000rpm.

Thanks for responding and appreciate any more insight.

Joe in St Louis
"Junkyard"
850T-Powered Ambo

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