Carb fine tuning

[TopCatGr58]

I think the test will be to drop the floats 2mm, to 21mm, and see what it does. I suspect it may clear up the low end, but take away from the top. If that happens, then going up on the mains should clear it.

Hey Cnuk,

I think you've got that backwards! Lowering the floats(upside down orientation) will RICHEN things, and if you are already too rich in the pilots, it'll worsen it. It may help the top end a little though. I didn't realize you were at 3500ft elevation. Yeah, I think the 45's are too rich also. I'm at sea level, and my STOCK 42.5's that came in my 81SH are just fine, and I've got thicker air down here!!

Good Luck, have fun, and keep us posted! T.C.

[Crazcnuk]

By 'dropping' the floats I mean lowering them so the fuel level will be lower in the bowls. I guess I meant 25mm instead of 21!

[Crazcnuk]

So I pulled them apart today, and found I had put the 42.5 pilots in last time!


So I dropped teh floats 2mm to 25mm, and put the 120 mains in.

The bottom end bog is gone and it doesn't 'load up' when pulling low speed maneuvers or driving at 2500rpm.

However, the top end is unchanged. It pulls past redline 1-3gear and will pull to redline in 4th, but 5th basically just sits where it is when you shift up from 4th.

The top end of this bike is effectively 180kph, it won't go any faster.

I am not too worried about it, as long as the mileage stays in the 40's it will be fine.

[DiverRay]

So run the floats UP 1mm, and try it. That SHOULD just about seal it!

[Crazcnuk]

Would seal what? Dropping them did exactly as advertised.

Going up from 110 to 120 mains did nothing for the top end, but the low and mid seem to be running well, and fuel economy is in the ballpark.

[Ivan]

I too have gone to the 42.5 pilot jets. As mentioned in a previous post, the idle needles are ineffective. There is still a noticable hesitation on mine, so I am going to up the size of the pilot air jet to see what happens.

I have also gone to the 120 mains, and I think that is just about right. I have gone through each size from 110 to 120. when I hit 117.5 I could back off the throttle a bit at high rpms without the bike surging. Now it is reallt smooth and pulls VERY nicely above 3000 rpm.

Hopefully I can get the low end to be nicee, cause I would hate fighting the air box again. I feel about the airbox the same as some feel about the octopus.

[drooker56]

The airbox or should I say poorly designed space theif was the bain of my existence. I converted to pods just so it would be easier to remove my carbs, i had been doing it so often.

I recently rebuilt my carbs with kits from ebay. I replaced every part I had been cleaning everytime I took it apart looking for what was missing and why it still wouldn't run right or start easy. Well, i finally found my problem, one of the jets in my kit I had never saw before. I believe its called the "slow jet", its the one under the screw. While working under bad lighting all the time I had never noticed anything in that hole and yes I had looked. Two of these jets were clogged and the third was mostly clogged. I replaced them with the new ones and she fired to life! With empyt bowls she only turned over 4-5 times and burst to life! I have never been so happy.

Just sharing one of my few success storys.

[bikerphil]

I would hate fighting the air box again

If you get rid of the top air box bracket and cut off the snorkel 1" from the base, the airbox can be removed easily first, before removing the carbs. I run both my bikes this way and it's soooo much easier to remove the carbs, not to mention possibly more airflow.

[Crazcnuk]

I can pop the carbs out in under 5 minutes, with the airbox in, so I don't find it anything to worry about.

It takes longer to take the seat and tank off!

I am goign to try it with the 120's for a bit and see how the plugs look.

I started another thread about these carbs coming with anything from 110-120 mains fromt he factory. I am wondering if, with carbs that have 110's and 120's in the middle, if we should be using the 120's as the base, not the 110s.

Maybe they put the smaller jets in the outer cylinders to get them hotter!

[Crazcnuk]

Current setup:

120 mains
42.5 pilots
51x11 needles
336-Y0 tubes
Floats 25mm

So far, smooth as glass from idle to redline up to 3rd gear. Pulls to redline in 4th, but sluggish 7000+ in 5th.

When cold will idle smoothly at ~600rpm w/o choke.

Added fuel filters and crossed the fuel lines (side to side) and put new vacuum nipple plugs on.

Also found and eliminated a cracked octy vacuum line.

[petejw]

Hey Craz,
Have u tried raising the floats to 23mm?
i think at 25mm you might be running on the lean side of things.

[Crazcnuk]

Heh, no I just dropped them as I was running too rich.

On the last trip I took I was getting soot collecting around the outlets of my mufflers, on the outside.

[Crazcnuk]

Took a trip today with Derwat. We filled up before we left and filled up at 152kms. We were within $.02 on our usage!

44.9mpg Imp

37.12mpg US.

This is cruising 110kph (68mph) to 120kph (74mph) With about 10kms of gravel, and a bit of hay field riding.

[Crazcnuk]

Derwat and I took another run to Jasper today.

Our mileage was fairly close.

He used 8.6litres over 157kms for 51.57mpg imp or 42.9mpg US.

I used 9.22litres over 163.5kms for 50.09mpg imp or 41.71mpg US.

The speed limit, in the park, is 90kph, so we were trying to stay at 100, but spent most of the time at 110, with the odd bits at 120kph.

I am going to repeat the run tomorrow.

We filled up at the same time and went the same distance, so the difference between our total distance has to be due to our speedos being slightly out with each other.

I also did about 60kms of the trip
in 4th gear....oops