Motor won’t go past 4000 rpms

[Gary pope]

Ok I have a 95 speedster with twin 657x motors in it but when I just took it out for it he first tine with brand new motors I installed in it and with all four carbs rebuilt one motor rubs don’t to the 7000 rpm mark but the other one will only get up to the 3500-4000 rpm mark and it smells of gas real bad and seems to bog down. Before installing it gagain motirs I did the ohm test on both ststors and they both were within specs. What could I be missing...?
This has got me stumped.. I just can’t seem to get the one motor past that 3500 rpm mark..

 

[mlcrew94]

Just following this thread as I’m having a similar problem.

 

[2x2smoke]

Spark plugs show too rich? Running on both cylinders? Compression normal? Choke and throttles fully opened by the cables?

Do all the sucking and blowing tests on the fuel supply and return lines to assess the proper function of the check valves.

If everything checks out so far I would swap carbs from good motor to bad and see if the problem follows the carbs. Others might suggest taking the bad carbs apart first to double check your rebuild.

 

[MONDELEZ]

Was there ever a s

Ok I have a 95 speedster with twin 657x motors in it but when I just took it out for it he first tine with brand new motors I installed in it and with all four carbs rebuilt one motor rubs don’t to the 7000 rpm mark but the other one will only get up to the 3500-4000 rpm mark and it smells of gas real bad and seems to bog down. Before installing it gagain motirs I did the ohm test on both ststors and they both were within specs. What could I be missing...?
This has got me stumped.. I just can’t seem to get the one motor past that 3500 rpm mark..

did you come to a conclusion to your issue ? I’m having a very similar issue with my 98 sportster

 

[Gary pope]

Yes I am 90% sure that something has to be wrong with the carbs. I do know from my experience is working on motors, when you put your hands over the carburetor there should not be spitting out a little bit of gas at higher PMs. Both motors and those are brand new with only about 15 minutes run time on them. As far as the plugs, I know it is flooding out for some reason because the spark plugs are black and fouled out, so what I did is I got the next hottest plugs, the BR7 ES and it ran a little better but it is still getting too much fuel for some reason. Like I said it starts fine and idles fine the issue is when you go to give it gas

 

[MONDELEZ]

Yes I am 90% sure that something has to be wrong with the carbs. I do know from my experience is working on motors, when you put your hands over the carburetor there should not be spitting out a little bit of gas at higher PMs. Both motors and those are brand new with only about 15 minutes run time on them. As far as the plugs, I know it is flooding out for some reason because the spark plugs are black and fouled out, so what I did is I got the next hottest plugs, the BR7 ES and it ran a little better but it is still getting too much fuel for some reason. Like I said it starts fine and idles fine the issue is when you go to give it gas

Hmm sounds very similar to my issue , I’m going to swap my carbs and see it it helps my issue . My issue accrued after I put it away for the winter . I fogged the engine before and now this season I’m having this issue . Please keep us informed if you get to the bottom this problem is driving me nuts

 

[Gary pope]

That’s exactly what I plan on doing tomorrow is swapping the carbs out to see if the problems travels with the carbs or if it still stays with the motor, to be continued.

 

[mikidymac]

Don't change to Br7ES plugs, that's not your issue it's the carbs.

 

[MONDELEZ]

Don't change to Br7ES plugs, that's not your issue it's the carbs.

I have 9s in there now , just finish swapping the carbs . Will test it tomorrow , engines are starting up fine the one engine which was running good is running a bit rough right now with the other carb, the carb that was on the bad engine. Will test under load tomorrow crossing my fingers . I will report back , thanks

 

[Gary pope]

My issues are not the carburetors because I swapped carbs from motor to motor and it still does the same thing, I switched to the BR seven ES plugs in it did run better you are fine to do that

 

[Gary pope]

I’m leaning more to the mpem

 

[2x2smoke]

That’s exactly what I plan on doing tomorrow is swapping the carbs out to see if the problems travels with the carbs or if it still stays with the motor, to be continued.

so it sounds like swapping carbs made no difference? Thats progress at least.

What does the compression test say? Positive that both cylinders are firing? Both plugs look the same? Temperature gun might detect a cold cylinder. Alternately grounding spark plugs might reveal a dead cylinder but...

I'd strictly follow the service manual if you are trying to chase down weak spark so you don't damage an otherwise good mpem. find out if yours has separate CDI modules which may also be swappable between motors.

Electronics going bad should not coincide with rebuilding motors so maybe more history would help

 

[Gary pope]

Swipe in the carbs did not help, same issue. I swapped the coils and it still does the same thing . I did and amperage test with a multimeter yesterday and found out that the port motor is getting considerably less amps in the starboard motor it will run and start fine on the trailer however when you put a load on it in the water that’s on the bogging issues take affect and won’t go over 3000 RPM’s

 

[JRB]

Is this a timing issue? Spitting is an off combustion ?

 

[MONDELEZ]

I just got out of the water and now I have both engine running a low rpms also accompanied by a new problem a steady beeping . Not sure if the beeping alarm is restricting me from Reving the engines or it’s a separate issue altogether . I’m ready to to sink this boat .

 

[Gary pope]

You were beeping alarm is your overheating

 

[MONDELEZ]

I was thinking that , so I unplugged them but the beeping still continued , also didn’t change my rpms on both engines .

 

[mikidymac]

The overheat alarm is just like an idiot light, it doesn't do anything to the way the engines run, just makes noise.

 

[MONDELEZ]

Hmm why would both engines now run low rpms now? Is it possible that the carbs need to be tuned . Also I was running the engines with the air box and filters off, could they be getting too much air ?also what would give me a overheating alarm? It was running the other day no alarm! Just swapped the carbs nothing else

 

[jhjesse]

Check the rectifier on that engine.
Check the pulse line and make sure it is not leaking/cracked or pinched.

 

[MONDELEZ]

Would the rectifier cause the overheating alarm or low rpms or both.

 

[Gary pope]

The overheat alarm is just like an idiot light, it doesn't do anything to the way the engines run, just makes noise.

Doesn’t it put it into limp mode though?

 

[JRB]

Hmm why would both engines now run low rpms now? Is it possible that the carbs need to be tuned . Also I was running the engines with the air box and filters off, could they be getting too much air ?also what would give me a overheating alarm? It was running the other day no alarm! Just swapped the carbs nothing else

The beep is a condition set by ty the sensors. Low oil pressure or over heat set the a alarm and puts the engine into low rpm to protect them. The sensors a are dirty or it’s the old style or the voltage on the charging system is low setting funny conditions with the computer. Check voltage replace both sensors I lived it !!!!

 

[mikidymac]

The beep is a condition set by ty the sensors. Low oil pressure or over heat set the a alarm and puts the engine into low rpm to protect them. The sensors a are dirty or it’s the old style or the voltage on the charging system is low setting funny conditions with the computer. Check voltage replace both sensors I lived it !!!!

That is not correct on these. There is no oil pressure on a 2-stroke. These only have an injector oil level sensor, overheat sensor and low fuel sensor and are just an idiot light. None of these sensors input into the computer and ther is no limp mode, just an idiot light that turns on.

 

[mikidymac]

Doesn’t it put it into limp mode though?

No, see post above, these do not have a limp mode.