Rich runner?

[SteveD]

My float bowls are clean, no dirt, no extra weight.
When removed carefully after a ride, taps off, the left weighs 169gms, the right 170gms. New bowl gaskets a month or so ago. Diaphragms seated well and not torn.

The fluid level is 14mm from the top edge.

I do get a petrol smell on the right boot after a long ride. I can wipe a film of petrol from the front of the bowl. No drips or leaks otherwise.

160 main jets, new needles @ 2nd notch, new needle jets 2.68. Bike starts easily, doesn't need much choke. At higher rpm in 4th or 5th it seems to struggle along, nqr. It can rev to redline. It struggled more in the mountains (over 1200metres) last weekend and was better, but not right, at lower altitude. Too rich? Change to 2.66 needle jets?

[moosehead]

What model/year bike Steve? 40mm Bings. Carb numbers?

I have an 82 RS with 40mm bings and rebuilt carbs this past winter with new needles and needle holders, Main unchanged. Diaphragms replaced as well. So almost dead on what you did. First ride this spring (yesterday) everything was fine but needed to rebalance and redo idle mixture as was stumbling somewhat on take off. After minor tweaks went for another run then did high speed cut off and pulled plugs...they were a tad rich maybe but overall ran fine. Sorry can't add much to your case.

Check fuel flow? Re-check diaphrams...pinholes sometimes hard to find...what about replacing diaphrams to see if any difference?

Fuel leak...I had a fuel line split at the carb fuel spigot once. Seemed like it was coming from the carb bowel but only after pulling the carb to do some other work I noticed the fuel line split. Changed out...no leak

[barryh]

The fluid level is 14mm from the top edge.

It struggled more in the mountains (over 1200metres) last weekend and was better, but not right, at lower altitude. Too rich? Change to 2.66 needle jets?

Better at low altitudes does sound too rich. What does 14mm from top edge translate to in actual fuel height in the bowl ?

[SteveD]

The fluid level is 14mm from the top edge.

It struggled more in the mountains (over 1200metres) last weekend and was better, but not right, at lower altitude. Too rich? Change to 2.66 needle jets?

Better at low altitudes does sound too rich. What does 14mm from top edge translate to in actual fuel height in the bowl ?

Just measured @ 26mm. Snobum suggests 28mm on a 40mm BING. I'm going to flush and refill the tank later today before work, then recheck when I get home from work late evening.

[Roy Gavin]

26 mm should work fine on 40 mm carbs but when my carbs are in spec and giving 20+ km/L I need a fair bit choke.

I find if I remove and check one side at a time there is sufficient vacuum in the system to hold the fuel in the line,but only if the bowl is replaced and the system refilled before the second one is removed.
2.66 jets work fine for me with the needle in 2 , and the later piston springs.

[moosehead]

Just checking specs on 40mm carbs...in a Haynes manual for what its worth...

UK (Euro) carbs #94/40/111 & 112
Needles position 3rd notch from the top

US models carb # 94/40/113 & 114
Needle position 2nd from top

All other specs re: needle jet sizes, needles and main all the same...just needle position different.

For Euro spec bikes wouldn't running needle position in 2nd notch down vs 3rd be richer running?

[SteveD]

For Euro spec bikes wouldn't running needle position in 2nd notch down vs 3rd be richer running?

2nd notch has the needle deeper into the jet, therefore leaner.
3rd notch has the needle raised higher, therefore richer.

The thing that makes me think it's running rich is it's performance at an altitude over 1200 metres last weekend. Usually this wouldn't bother this bike. It didn't want to go at higher speeds, but performed better at lower altitude. It still wasn't normal though, feeling "rough" at 60-70 kph suburban riding, like the choke was still on, not like surging if lean.

Oh, and a smelly right boot.

If I put the straight thru Jim Crays on it, without going for a bigger MJ, I wonder if it'd work better? That'd just be ignoring the current issue I'm afraid, but tempting.

[ME 109]

Can't offer much Steve, maybe there are other issues causing it? Timing, valves, advance mechanism?
I've never noticed any problems due to our altitudes.

[SteveD]

Can't offer much Steve, maybe there are other issues causing it? Timing, valves, advance mechanism?
I've never noticed any problems due to our altitudes.

I haven't either. That's why I thought that it might be a bit too rich to begin with, or choke doing something because it did seem worse up higher especially between Adaminaby and Kiandra. It still doesn't feel right though.
Valves were set not long back. I could check them again. I usually go somewhere from 0.12 - 0.15 IN to 0.16 - 0.18 EXH. L&R equal of course.

Plugs have black soot peripherally, but the electrode looks ok.

My thoughts lie towards:
1. float height. Must be marginal though
2. jetting or needles. The right needle was giving me trouble 'cause the clip was dodgey. Replaced that and it's now well held in position.
3. choke. It starts without choke mostly. During the initial warmup ride it is sluggish, which would be normal, but when warm it feels similar when holding a constant throttle at 60-70 kph suburb speeds. The screws are tight on the choke cover, but I've never had them apart so maybe a gasket deterioration?

The slower running issue might be the 2.68 needlejet (1 size bigger than 2.66 stock) but I doubt it. That might be an easy substitution to try. Or a choke problem. That'll take a bit longer. A job for the days off which will be Friday & Saturday. Then I'm on nights and don't use the bike for work so I'll try that then..

The faster running issue would normally be the MJ. It struggled to pull over 5500rpm in 5th. Redlined ok in lower gears. Was thinking diaphragm, but they were ok. There was some crud in the left bowl. MJs and jet stacks were clear however. No rubbish occluding anything. I've had that issue before, but it is a different feel as one cylinder would normally be involved. I drained and flushed the tank yesterday.

Fuel hoses don't leak either so that isn't why the right boot stinks. That issue only became apparent on the long weekend ride. Doesn't seem an issue on shorter rides.

[dwerbil]

Can't offer much Steve, maybe there are other issues causing it? Timing, valves, advance mechanism?
I've never noticed any problems due to our altitudes.

I haven't either. That's why I thought that it might be a bit too rich to begin with, or choke doing something because it did seem worse up higher especially between Adaminaby and Kiandra. It still doesn't feel right though.
Plugs have black soot peripherally, but the electrode looks ok.
My thoughts lie towards:
1. float height. Must be marginal though
2. jetting or needles. The right needle was giving me trouble 'cause the clip was dodgey. Replaced that and it's now well held in position.
3. choke. It starts without choke mostly. During the initial warmup ride it is sluggish, which would be normal, but when warm it feels similar when holding a constant throttle at 60-70 kph suburb speeds. The screws are tight on the choke cover, but I've never had them apart so maybe a gasket deterioration?

The first part of number 3 reminds me....some years ago, I had a idle problem on my R100RS, and this was after adjusting the carbs. The bike seemed to not need choke as much as it used to. I posted here that the bike would idle perfectly until it warmed up. Then, when at operating temps, it would cough/sputter at idle. Rob Frankham nailed it with saying I must have not had the engine up to proper operating temp when I set the carbs.

After reading his response, I did a twenty minute run on the highway and then set the carbs. That cured the problem. Whether or not this is related to your problem, it's at least something to keep in mind when setting carbs -- getting the engine up to operating temps.