90 fzr600 carbs...
Moderators: Site Director, FZR Forum Moderators
-
turbospark
- Site Newbie
- Posts: 7
- Joined: Mon Oct 08, 2012 8:56 pm
- Location: P.R. USVI
90 fzr600 carbs...
Hello there guys...just a question that I have...the carbs on the 90 fzr600 are supposed to be 38mm mikunis if I'm reading correctle from the specs sheet of the bike...Wouldn't they flow better than say a set of 32's, 34's, 36's? the bigger the more airflow...so if this is true, why couldn't I use the cylinders, rods, pistons, and heads from theyzf but keep the fzr carbs...?
1990 Fzr600
1985 ZL900
1985 ZL900
-
yamaha_george
- 5000+ Posts
- Posts: 5853
- Joined: Fri May 09, 2008 8:46 am
- Location: west london UK
Re: 90 fzr600 carbs...
hi,
You are only looking at a tiny part of the whole engine air flow function by just considering carb venturi size.
Just consider the carb is only acting in concert with the valve opening time and the air flow round the valve head port and the suction created by piston head decending PLUS how long the exhaust port is open while the intake is open and the air flow both IN & OUT round that valve head.
Then ther is the efficiency of the down tubes and the rest of the pipes + the efficientcy of the "silencer" box.
Get any mis match and fuel economy engine efficiency go AWOL, NOW spread that over the rev range to multiply the "mis matches" that exist because of all of this moving feast of data.
If you want a quick example remove the air box and mount filter pods to the carb mouth you will NEVER get a decent state of tune simply because the air inlet tract is now shorter & there is a metal wall at the end of the pod to give harmonic fuel echoes.
Then add plastic plumbing pipe stalks to the carb mouththat are eqal in length to the original air box rubber pipes and mount the filters on those, suddenly a decent tune up with no flat spots is possible.
In the WIKI tech book & links section are several links to exhaust pipe D shape designing read it thro & try not to let it give you a headache <BG>
One tip IF you decide to experiment keep VERY DETAILED notes and share them that way we can look at your stuff and maybe match it close to ours and be able to point you to a reasonable result JUST MAYBE............
You are only looking at a tiny part of the whole engine air flow function by just considering carb venturi size.
Just consider the carb is only acting in concert with the valve opening time and the air flow round the valve head port and the suction created by piston head decending PLUS how long the exhaust port is open while the intake is open and the air flow both IN & OUT round that valve head.
Then ther is the efficiency of the down tubes and the rest of the pipes + the efficientcy of the "silencer" box.
Get any mis match and fuel economy engine efficiency go AWOL, NOW spread that over the rev range to multiply the "mis matches" that exist because of all of this moving feast of data.
If you want a quick example remove the air box and mount filter pods to the carb mouth you will NEVER get a decent state of tune simply because the air inlet tract is now shorter & there is a metal wall at the end of the pod to give harmonic fuel echoes.
Then add plastic plumbing pipe stalks to the carb mouththat are eqal in length to the original air box rubber pipes and mount the filters on those, suddenly a decent tune up with no flat spots is possible.
In the WIKI tech book & links section are several links to exhaust pipe D shape designing read it thro & try not to let it give you a headache <BG>
One tip IF you decide to experiment keep VERY DETAILED notes and share them that way we can look at your stuff and maybe match it close to ours and be able to point you to a reasonable result JUST MAYBE............
