1988 Elite SA50... runs better at 3/4 throttle then at full

[ramblerdrver]

Recently aquired a 1988 Elite LX SA50. Looking forward to some "tinkering fun" this fall & winter. It's in good condition and is complete. Speed tops out at 30mph at about 3/4 throttle...but at full throttle, the same 30mph! Engine feels and sounds good at 3/4 throttle but flat and "sour" at full throttle. I've installed a new air filter element (it had none in the air cleaner when I got it and it would barely reach 20 mph that way and felt like it was running "rich"). Spark plug looks good. I tend to think the problem might be a dirty carb or plugged exhaust (or spark advance?), but thought I'd ask here if anyone had an idea what to look for before doing any disassembly. ???

On a somewhat related question (which may more properly go in another forum heading)...if I install a "free flow" air filter and remove the exhaust restriction or get an aftermarket muffler, is a larger carb main jet required?

Thanks for any help!

[Bear45-70]

Do a plug chop at 3/4 throttle where it is running good, then do one at WOT where it runs like crap and report the results. I would suspect that it is going lean if you are not runnng the stock air box and filter.

[ramblerdrver]

Do a plug chop at 3/4 throttle where it is running good, then do one at WOT where it runs like crap and report the results. I would suspect that it is going lean if you are not runnng the stock air box and filter

I feels like it's lean at full throttle...no getting enough fuel. It does have the stock air box and filter element. When doing a "plug chop" test, how far (or long) can you safely run at full throttle if it's running lean?

Thanks

[Bear45-70]

Do a plug chop at 3/4 throttle where it is running good, then do one at WOT where it runs like crap and report the results. I would suspect that it is going lean if you are not runnng the stock air box and filter

I feels like it's lean at full throttle...no getting enough fuel. It does have the stock air box and filter element. When doing a "plug chop" test, how far (or long) can you safely run at full throttle if it's running lean?

Thanks

30 seconds should color the plug.

[ramblerdrver]

Took the Scoot out today to do a plug chop....and of course it ran fine...35+ full throttle! Did do the check with a new NGK plug and it showed the beginning of a slight gray/tan deposit on the center electrode. Later it did have a period where it ran rather poor and had trouble getting much past 25...but then it mostly cured itself and then ran okay. Figure the next step is to clean the carb and make sure the fuel filter is not plugged.

Does this model (1988 Elite 50 LX) have a speed/power restriction somewhere? Exhaust...intake...timing? Does the variator drive pulley have a limiter on it so it won't achieve full drive diameter?

Thanks

[Bear45-70]

You are too lean, fatten it up at least make sure the float level is right and you have the right jet in it. Gray is gonna melt your piston for you eventually.

[Wheelman-111]

Greetings:

Actually, even an unrestricted SE/05 is doing pretty good to run much above 35, or such was the case with Flash I, a stock '87 Aero with pretty much the same engine as yours. Start with a clean air filter and decarbonized (if necessary) exhaust. Add an aftermarket variator and you should see 40-ish.

[ramblerdrver]

You are too lean, fatten it up at least make sure the float level is right and you have the right jet in it. Gray is gonna melt your piston for you eventually.

Took off the carb today and disassembled it...found lots of fine particals in the float bowl...looks like fine rust. So guess it's time to clean the carb and fuel tank and filter. I was surprized to find it has a steel tank, was expecting a plastic fuel tank like the oil tank.

The main jet is a #88, like it should be. I'd like to try something slightly larger, like a #90. Who is a good source for these jets?

I also removed the muffler and found it doesn't have a restrictor in it. Since the engine started and idled fine, I don't think the muffler is plugged with carbon. But I read somewhere on here that one way to check it is by weight. The number on the muffler is ...HMGS7-Honda-Sankie-2091. Anyone know what the max weight should be (with or without the heat shields?)?.

Thanks