The Exhaust Thread

[Drunkn Munky]

It looks like 3/4 system as the front downpipe are shorter than standard. But it is possible the front pipes have been cut down.

More pics;




















Any ideas??
The endcan is unbranded and as the exhaust has spring eyes for an end can i assume its not original to the exhaust

Cheers

Jeff id say that the stock front pipes have been cut and a new section put in there to join them to the system, no idea what the system is but only a few route that way, micron, two bros.

[Viffer]

My 1992 NC30 has an aftermarket LeoVince silencer. Great sound but the jetting is bad, the mix is bad, too much gas between 5.000 and 6.000 rpm. So I bought a Dyno test to get the carb jetted but the guy told me it's impossible for him to jet correct since the silencer doesn't fit the flow.. Is this really true? Do you have any ideas? Should I find a used stock silencer (I don't have one) or buy another aftermarket silencer? Thanks!

Your silencer doesnt fit the flow??? Sounds like your dyno guy doesnt want to do it hence fobbing you off. If your confident pull the carbs off yourself or dind another dyno guy

He said something about the silencer drags air back into the engine or something, I'm not an expert, I'm sure you can tell.. Also, he could fix the mixture between 5 and 6.000 rpm but then the other rpm area would be screwed. Do you think I should try buying a used stock silencer? Or try another aftermarket silencer? Thanks!

[skinnydog0_0]

My 1992 NC30 has an aftermarket LeoVince silencer. Great sound but the jetting is bad, the mix is bad, too much gas between 5.000 and 6.000 rpm. So I bought a Dyno test to get the carb jetted but the guy told me it's impossible for him to jet correct since the silencer doesn't fit the flow.. Is this really true? Do you have any ideas? Should I find a used stock silencer (I don't have one) or buy another aftermarket silencer? Thanks!

Your silencer doesnt fit the flow??? Sounds like your dyno guy doesnt want to do it hence fobbing you off. If your confident pull the carbs off yourself or dind another dyno guy

He said something about the silencer drags air back into the engine or something, I'm not an expert, I'm sure you can tell.. Also, he could fix the mixture between 5 and 6.000 rpm but then the other rpm area would be screwed. Do you think I should try buying a used stock silencer? Or try another aftermarket silencer? Thanks!

Where abouts are you located? You need to take it to a dyno that knows what they are doing with these bikes. The 5k 6k at spot is normal, he should be trying to get the whole curve as smooth as possible. The end can doesn't drag air back but it will create back pressure pulses that affect the engine. This is more important on 2 strokes and unless you are running a top spec race bike I doubt it would make too much difference. The end can u have will be much much better than standard.

[Viffer]

I appreciate your help. I'm in Copenhagen, Denmark, and the Dyno guy is very famous for his excellent skills around here. He has been doing carbs and injection bikes for 30 years. But I'm starting to mistrust his conclusion on this one.

I'm not confident taking off the carbs myself so my idea was to bring it back to stock, i.e. buy a stock exhaust and a stock air filter (not sure whats on now) and then the problem would be solved.. But you're tellign me the LeoVinci end can is better than stock. How do I fix the problem with bad air/fuel mix (too much fuel) from 5.000 to 6.000? Thanks!

[Viffer]

one more

[skinnydog0_0]

I don't doubt the guy's ability at doing dyno's but compared to an inline 4 these bikes can be very time heavy to work on and quite tricky/fiddly. To try and get rid of mid range dip, use a 0.5mm washer under your needle this should help.

[CMSMJ1]

that system ofyours is strange Jeff.. Looks like a DIY job under the front...

that Danish jetting is just a touch out- Needles can be changed with the carbs on the bike..so get a chekc on the washers in there.

if it is going to 10:1 air to fuel then that is already rich is it not? surely we want it to be leaner in that area, so fewer washers and if that makes it leaner all over, then good?

[skinnydog0_0]

that system ofyours is strange Jeff.. Looks like a DIY job under the front...

that Danish jetting is just a touch out- Needles can be changed with the carbs on the bike..so get a chekc on the washers in there.

if it is going to 10:1 air to fuel then that is already rich is it not? surely we want it to be leaner in that area, so fewer washers and if that makes it leaner all over, then good?

Yes I thought it may be made from a few different exhausts.
I can't see proper dyno graphs in full as I am on my phone, but would agree with you from your view of them.

[Viffer]

that system ofyours is strange Jeff.. Looks like a DIY job under the front...

that Danish jetting is just a touch out- Needles can be changed with the carbs on the bike..so get a chekc on the washers in there.

if it is going to 10:1 air to fuel then that is already rich is it not? surely we want it to be leaner in that area, so fewer washers and if that makes it leaner all over, then good?

I see why these bikes are hard to work on. You say remove washers under the needle and skinnydog0_0 says put one under. I'll talk to that Dyno guy and persuade him to try again.

[skinnydog0_0]

Listen to cmcmj1 he knows his stuff. I can't see the graphs full size so just assumed it was lean