Motor surge

1973 1600cc. problem is engine surges in low gear at low RPMs. High RPMs and uper gears motor runs fine. Have checked timing, vacume leakes, checked needle valves in carb, but has not checked preasure from stock fuel pump because of not having a guage. Any ideas on what may cause the surge. Considering electric fuel pump. Any ideas? I appologize for any miss spelled words, but I'm asking for a friend and he was telling me while I was typing and we're both old. He is a pretty fair mechanic and will probably understand any ideas. Thanks for your time.

[QUOTE=sonny8l3;767139]1973 1600cc. problem is engine surges in low gear at low RPMs. High RPMs and uper gears motor runs fine. Have checked timing, vacume leakes, checked needle valves in carb, but has not checked preasure from stock fuel pump because of not having a guage. Any ideas on what may cause the surge. Considering electric fuel pump. Any ideas? I appologize for any miss spelled words, but I'm asking for a friend and he was telling me while I was typing and we're both old. He is a pretty fair mechanic and will probably understand any ideas. Thanks for your time.[/QUOTE]

Directly under the carburetor there is electromagnetic plunger with only one wire going to it (It is a fuel cut off )sometimes It could Cause what you described...

Check motor mounts, These are stressed from the natural conversion to a trike.

does the horn ever honk in a turn or taking off?

first thing, I would get that fuel pressure checked. All I can add to the above comments, is to check for sticking pcv valve and loose carb screws and linkages and hanging EGR if you have one. Last resort, look at a carb rebuild?

Good hunting!

Several things.

#1...rubber boots on intake.

#2... dirty ports in carb.

Are the primary most possible problems.

And then plenty other.

Too much fuel.....sinking float, needle and seat, too much fuel pressure.

Too little fuel.....fuel filter, fuel pump, water,

Worn distributor....advance plate wobble, missing advance springs, vacuum diaphragm, leaking vac advance hose, vac advance hose on wrong port.

[QUOTE=rhino 2;767140]Directly under the carburetor there is electromagnetic plunger with only one wire going to it (It is a fuel cut off )sometimes It could Cause what you described...[/QUOTE]

Check for consistent voltage on wire to plunger when running. Flaky connection will cause rough idle and cut off. An old "get you home" fix for a bad fuel cutoff was to remove the wire and turn the unit out about a turn and a half. Reconnect the wire to keep it from twisting out any farther and drive home. If I remember correctly, it only come into play with the idle circuit so off idle performance shouldn't be affected.



Too little fuel will cause you to "run out of gas" when cruising and accelerating. After sitting on the side of the road for a minute or two, everything will go back to "normal" until you "run out of gas" again.

Hook up a dwell meter and check the points for dwell change

Have you recently done any tune up work to the engine IE points and or condenser?

From what I have just read, you have a good check list to go thru that should help solve the problem.

I had read about the old stock fuel pumps, not the best design, but it worked for the most part.

My trike was already upgraded to electric fuel pump, and now there is better ones on the market, so they claim.

The fuel pressure gauge, do not get a fluid filled one, unless you live in a steady temperature area. I got one and it works correctly in the warmer weather, not worth much in cold weather. Nevada cold in am and warmer in afternoon.

I will upgrade the fuel system soon.

Hope you can find the issue and resolve it. Keep Safe

Sonny, is this more of a jerking from loose driveline?

Hello, He checked every thing suggested. It turned out to be a broken tranny mount. He found it looking for some thing else. He said he fixed the mount and the scooter runs as it should. Thanks for all the help and your time.

[QUOTE=sonny8l3;769153]Hello, He checked every thing suggested. It turned out to be a broken tranny mount. He found it looking for some thing else. He said he fixed the mount and the scooter runs as it should. Thanks for all the help and your time.[/QUOTE]

ThumbUp..............

A tranny mount, that is crazy, but one to add to the book of things to check. I am glad to hear you have it all working now.

If you engine is non USA, mainly from Mexico, than it should be a 50hp. I was looking at engine numbers again and found mine to be this 50hp engine, that is if the chart was correct, LOL.:D

I am going to do a little clarification on this.

Typically "surging" means up...down...up...down.

A bad or missing bowden tube.

[ATTACH=CONFIG]89921[/ATTACH]

[ATTACH=CONFIG]89922[/ATTACH]

Usually make more of a single surge. As you release the clutch and the engine torque pulls away from the cable it open the throttle and as the acceleration setts and the engine torques back down the closes the throttle.

So this feels more like a zoomy start off.

I suppose that if you had an extremely bad engine/trans mount and it was all flopping about while driving it could feel like a surging engine problem.

So when you are trying to diagnose.... See if it is a zoomy start off or an engine surge at cruise.

By the way.....clutch chatter is usually bad or missing bowden tube or bad motor/trans mounts.

And also the throttle is usually a non issue on a trike as we typically use motorcycle cables and they do the same thing as a bowden tube.

Hello Jack, I tried to accept, but it says that I'm not allowed to talk to you. I'm tech stupid so I don't get the how come. But thanks ant way.

[QUOTE=sonny8l3;774401]Hello Jack, I tried to accept, but it says that I'm not allowed to talk to you. I'm tech stupid so I don't get the how come. But thanks ant way.[/QUOTE]

Hi Sonny, it looks like you have resolve on your problem;)