Topic: 750a wont run off idle

[notn]

I have a 750a  ( wheelchair accessable trike project) and we are having problems withe the bike at idle runs smooth, if you giv it ANY throttle it just dies.  I sounds like it just isn't getting any fuel.  We have checked all the carbs and float levels this is what we have checked and results
carbs--cleaned all ports and set floats., accilerator pump does not seem to work but even if you real gently try to giv it gas it dies and I thought all that pump did was give it an inital burst of gas.
inigion...we have spark at all plugs although not as healthy as I would expect, would condenser or coil cause a compleat death like no fuel? the plugs looked dry.
The bike run fine last fall when we quit work on it for the winter (my shop has no heat)....anyway thanks for any ideas ...Neal (pics on notn.org)

[raymond10078]

What did you do to clean "all ports"?

Did you remove the emulsion tubes?  The jets?

Timing set ok?

[77Pinto]

I agree that it could be a timing issue.  Check not only the static timing, but the advance.  I like to use the static method to set it, then a timing light to check both idle and full advance.

It could also be that you are not running on all four, as I have had bikes do what yours is doing and turned out to be running on three.  I like to use a little brake cleaner on the exhaust pipes to see if it REALLY is running on all four.

Have you tried putting the choke on and then attempting to bring up the RPMs?  Fresh gas?  Clean fuel filter?



Bill

[notn]

Thanks for the replies
By all ports I mean all the passages in the carbs that transfer air/fuel.  Timing was checked static anyway.  The one vacume tube that I assume goes to the airbox was plugged off when I got the bike (run fine then). All 4 cyl were firing at idle and it has to have the choak on to even idle untill motor gets warmed up then will idle without choak but try to advance the throttle with either choak on of off it just dies.  I have new condensers coming and will go over the whole timing/points system again.  My clymers book is a little weak in terms of explaining things to my little pea brain.  again thanks for the help.
neal

[raymond10078]

For the sake of clear communications:

Did you remove the main jet, and make sure it was clean/clear?

Did you remove the emulsion tube, and make sure it was clean/clear?

[TwoTired]

accilerator pump does not seem to work

Fix this...
 ...so the squirt jets shoot 6 or eight inches.

[77Pinto]

...... The one vacume tube that I assume goes to the airbox was plugged off when I got the bike (run fine then).....

If its a 78 the bowl vents connect to a vac hose that bolts to the top of the air cleaner box.  If this is pluged you will have problems.



Bill

[Spanner 1]

No accelerator pump operation = instant die when throttle turned off idle , sad but true Happened on my A...... nozzles quit squirting. Need to remove the airbox and examine the nozzles for spray with the carbs full of gas ( bike running or not, doesn't matter once bowls are full )....... most frequent cause of failure is the check valve at the bottom of the acc. pump 'sump' below #2 carb... plenty of info. , do a search... 

[notn]

Again thanks everyone for the info.  Found the problem it was a stuck ball and spring in the accilerater  pump and the two little holes in the diaphram was compkeaty swolen shut.  opened them up and cleaned that little sprig/ball check valve thing and got it all back together and  runs fine comes off idle fine.  Sure is a cold blooded thing tho.  I got to ride it for about 3 1/2 miles this evening befor the rain set in.  It sure isn't very quick heh heh, Me, the wheelchair, all the extra "bike" to make it wheelchair friendly has added a ton of weight.  I just want to putter around here local with it so no need for a 70mph light -to- light racer, got all that out of my system years ago. but sure was fun to ride again, looking forward to some short rides this summer. It is much more stable than my side car ( wheelchair )  setup I had on the tx650 yamaha here a few years back, thanks again
neal

[Dave B.]

I am a new 76 750A owner with all of the same problems as mentioned in this post.I did the carbs. cleaning and also found the accelerator pump blocked the same way.I would like an explanation about the brake cleaner test to check if the cylinders are firing. My bike is still breaking up under a load. (riding accelerating). I am going to pull the plugs and check for fire characteristics too.Someone please respond.

[raymond10078]

I would bet that brake fluid cleaner is sprayed on the exhaust pipe to check that they are all about the same temp (too hot to touch).

Have you performed a tune-up?  Unless you do a tune-up, you could be seeing multiple overlapping issues.  Best to start with a tune-up before you spend too much time trying to find that gremlin.

Also when you did the carbs - did you remove and clean the slow jets and the emulsion tubes?

[dave the welder]

its been covered elsewere here but you might want to check out swapping to a set of round top carbsoff a 71-76 750 they really woke up my 77.its starts easier idles better and seemslike it has a little more power.i would never swap back now the bike is a lot more fun to ride