Topic: Fuel/Air mixture

[Scout]

Hi, it's me again....

Short recap: 750K8, adjusted valves, cleaned the carbs, adjusted float level, replaced float needles, synced the carbs, set timining and cleaned the points, and put new D8EA plugs in, as well as a new air filter. Bike has 4-into-2 aftermarket exhaust, and according to the work order from '96, it was rejetted.

After doing all of that, my bike would not idle very well (rough) and #4 exhaust header wasn't getting as cold as the rest. Also, my two exhaust pipes would never get very hot. Even after a 2 hour highway ride, they would be warm, but easly touchable.

Anyway, I took the carbs out again, and cleaned them again. I made sure that I paid particular attention to the float needles, etc. I also, for the first time, adjusted the mixture screws to 1 1/2 turn - they were originally set at a little over 2 turns. Put everything back together, and here are the symptoms now:

1. The bike warmed up very quickly (I guess that's good, just not used to it )
2. The revs don't drop like they used to - meaning that if I let go of the throtle, they will slowly drop to idle. Could it have something to do with the accelerator pump, as in me not putting it together correctly? I think I adjusted the cables correctly, I can't really see doing anything wrong there...
3. After a 5 min warmup, and a 5 min ride around the neigborhood, the exhaust ends were very hot, I could barely touch it.
4. The bike sounds different, but seems to be riding a lot smoother than before, although I haven't taken it out on a longer ride yet, because I'm afraid that it is too lean...

Please help, and thanks as usual!

Scout

[jdpas29]

if the bike was rejetted, you may look into getting it back to stock.   drop your float bowls and check the main jet for a number around the rim.  with the setup you have, the stock 110 main will work the best. 

you can test your cables to make sure they are not a problem merely by taking them off one at a time and checking for binding.  if the cables aren't routed appropriately it can cause binding and a slow release to center.  if your cable is snapping back really quick but the throttle "sound" lags behind, your problem is elsewhere.

also...  did you set the gap on your points using TDC per the manual?

[Scout]

Well, the main jet works at higher throttle openings, as I understand it, and that part is not a problem. If my thinking is correct, the mixture screw effects the idle tp 1/4 throttle, right?

As far as the cables, there is no binding, and the throtle snaps right back. I've taken the carb off about 4 times now, and it hasn't been a problem - until now....

Scout

[TwoTired]

Short recap: 750K8, adjusted valves, cleaned the carbs, adjusted float level, replaced float needles, synced the carbs, set timining and cleaned the points, and put new D8EA plugs in, as well as a new air filter. Bike has 4-into-2 aftermarket exhaust, and according to the work order from '96, it was rejetted.

 here are the symptoms now:

1. The bike warmed up very quickly (I guess that's good, just not used to it )
2. The revs don't drop like they used to - meaning that if I let go of the throtle, they will slowly drop to idle. Could it have something to do with the accelerator pump, as in me not putting it together correctly? I think I adjusted the cables correctly, I can't really see doing anything wrong there...
because I'm afraid that it is too lean...

A. You said you synced the carbs.  But, did you do it after the last carb installation?
B. Have you checked the carb intake couplers for air leaks?
C. Maybe I missed the statement.  Are all your head pipes now at even temps?
D. Stock paper air filter?
E. If you are worried about too lean, check the spark plug center electrode insulator for deposits.  If it's white or no deposits, you could be too lean.  See  http://www.dansmc.com/Spark_Plugs/Spark_Plugs_catalog.html
F. The carbs on your bike were originally set up to run lean.  Further, the Idle Mixture Screws meter fuel and have a limited range of adjustment.  They may not have much effect at all, above 1/8 throttle on these carbs.
G. Return to idle issues might be sticking timing advance weights, slow to retard the timing at idle.  Check those for free movement.

Cheers,

[eldar]

well scout a big piece of advice is to get a dwell/tach if you still have the points. Use the dwell to set the points gap, MUCH more accurate than trying to use feelers as you can get the dwell identical on both sets. Now I dont see the reason why the PO rejeted as most 4-2 do not require it but as tt asked, are you using the stock filter? IF so then rejet should not have been needed. If you have the 110s, I would put them back in, unless there has been engine work done

If you are concerned about running to lean higher up, then get some thin washers and put the under the eclip that holds the needle. this will raise the needle kinda like the earlier 750 carbs. 

As for the accel pump, it only pumps a small amount of fuel and I do not think it is under constant operation, it is only for accelerating from idle to avoid flat spots. It should however be adjusted. the pump rod should not contact the actuator tab when at idle, there should be a small gap.

do a sync again as tt said if you have done any carb work since the last one. then use the dwell/tach while adjusting the low speed mix screws. Remember on the 78k out is richer and in is leaner since these are fuel screws. the tach will allow you to adjust much better than any ear can hear.

[Jarkko68]

Hi!Have you checked advance unit behind pointer plate?It's making problems when rusty and sticking.

[Scout]

Hi Guys,

Thanks for resurecting my thread, I was loosing hope In fact I used that as an excuse with my wife to buy a new car, so I'm driving a new Crossfire Roadster 6-speed as of last Sat Anyway, to answer some of your questions:

1. I replaced the Honda filter with a paper Emgo filter, so I don't think there would be a difference there.
2. I did not re-synced the carbs again after the last carb demout/mount. I will do that again.
3. No vacum leaks, checked with WD40.
4. Checked the plugs, no deposits whatsoever on the ceramic part.
5. Yes, all pipes are equaly scortching now

I have purchased a new Honda points plate, and will get a tach/dwell meter to get it properly installed. I will also do the carb sync again, and see what happens. If that doesn't help enough, I will turn the mixture screws out to it's original setting of 2 turns. Hopefully that will be enough... I will report with results....

Scout

[eldar]

The emgo filter is a bit more free flowing than the honda filter I think but should not make a HUGE difference. Do your sync and that will help but that low speed will be off unless you use a dwell meter or do butt-loads of plug chops.