1998 Elite SP50A Issues

[FredB32]

Hi all - first post, so thanks in advance for any help you can provide.

I've got a 1998 Elite I'm working on for a friend and am a little stumped right now. I think I have a couple things to check/re-check but thought I'd touch base with the experts before plowing forward.

The issue: motor starts up perfectly fine when cold, gets up to operating temp (cold idles up to about 1,900-2,000 rpms) and then sputters down to 600-800 rpms for a short bit and conks out. Giving it a little throttle bogs it down worse. It will start up again, but right back to low-rpm idle, or if left for a few minutes, does the same scenario outlined above. It does seem to burn/smoke more than I would expect as well, particularly once it's warmed up.

Here's what I've done to date:

-Took off and cleaned carb, soaked in cleaner, ran my wires/brush through all the ports/jets
-Replaced fuel filter
-Took off and cleaned the fuel petcock per the service manual, confirmed the fuel and vacuum lines were clean/clear
-Replaced air filter (new OEM)
-Check bystarter resistance (~4.1 Ohms)

My best guess here is it's a fuel issue, based on the fact once it's warm it drops the idle rpms. The bystarter resistance checked fine, as I mentioned, but I'm wondering if it might still be the issue and if I should just replace it. Based on the above, is there any other thing I should/could check or any other info that may be helpful? I've been reading about the reeds but haven't got that far yet to look at them. I would need to find a 12v battery to test the needle movement on the bystarter. The carb overall looked really good, and I believe it's the original as well.

Thanks all!

[motormike]

The bystarter will produce those symptoms if it is not completely shutting off the cold-start circuit after warming.
Also, slow fuel delivery /recovery will do the same thing.

[FredB32]

Thanks Mike - sounds like it's likely the bystarter is the issue. Any recos for a reasonably-priced option? I'm sure, knowing Honda, that OEM is the best way to go, I'm just not sure how much they want to put into the moped.

Also - could you expand on this more? Is there something else I should be considering or looking at?

"Also, slow fuel delivery /recovery will do the same thing"

[motormike]

Can't make a recommendation. sorry.
Does petcock flow fuel in a good strong stream when vacuum is pulled on the hose to the intake ?
Are fuel lines new ?
Is vacuum line new ?
Is float needle good ?
Have you checked fuel level in float bowl when it bogs and dies?
Try some of this stuff.

[Meatball]

I had a float needle go haywire on me once. The tiny spring loaded nipple was stuck OUT and took force to finally get it to push in. I figured it was gummed up from old varnish fuel so I soaked it and got it working freely...I thought. Motor kept dying out so I pulled the carb apart again and the nipple was stuck IN this time! I finally replaced the sombich and ran great.

Also check to see if the float actually still floats. Ive never had a cracked one but Ive heard about em.

[FredB32]

Thanks guys. To answer questions:

Does petcock flow fuel in a good strong stream when vacuum is pulled on the hose to the intake ? - I can't say for sure. I've seen in the service manual there's some sort of tool to supply this, and I've also read to just suck on it? lol...it had a little fuel in the line when I pulled it (is it supposed to?) so I'm not certain I want to suck on it with my mouth (that was painful to type out). Is the fuel in the vacuum line a potential issue?

Are fuel lines new ? - definitely not! They all appear to be in good shape (i.e. no leaking) and are flexible.

Is vacuum line new ? - same as above

Is float needle good ? - it looked fine when I pulled it all apart (i.e. looked pretty new and shiny). The float seems to work just fine, although about half the carb diagrams I can find show the needle with a little (spring?) tab as part of the assembly...which if there's supposed to be one, it's definitely not there.

Have you checked fuel level in float bowl when it bogs and dies? - I have not. Is it as simple as just opening up the bottom drain hole after it dies? This is my first moped I'm working on, so somewhat all new to me.

"I had a float needle go haywire on me once. The tiny spring loaded nipple was stuck OUT and took force to finally get it to push in. I figured it was gummed up from old varnish fuel so I soaked it and got it working freely...I thought. Motor kept dying out so I pulled the carb apart again and the nipple was stuck IN this time! I finally replaced the sombich and ran great."

-it looked fine to me when I pulled it out, and when all back together the float itself had some spring bounce to it, but I'll pull it apart again when I have a chance and double-check everything. By the spring, are you referring to something built-in to the needle itself?

"Also check to see if the float actually still floats. Ive never had a cracked one but Ive heard about em."

-the float didn't have any fluid in it and seemed perfectly fine from what I could see.

[Meatball]

The float needle (metal end) has a spring loaded peg protruding from it. You should be able to use a pointy tool and press down on it a few times to see if its moving freely and springing like it should.

The rubber tip end should also be inspected for wear/damage. Over time, the rubber degrades and becomes mis-shapen. It need to make an absolute positive seal in the needle seat. Needles are like $5 so if theres any concern...replace it.

Needle seat: this can get gummed up for various reasons. Even corroded and damaged beyond repair. Theres info/pics about it in the carb cleaning tutorial of the wiki.

Carb gaskets: sometimes leaky carb gaskets dont actually leak fuel out...but suck air IN during throttle. I always replace the rubber in old carbs just because. Find the right kit and it includes bowl gasket, intake o-ring, bystarter o-ring, etc...like $20.

[Meatball]

Crank seals can do the same thing. Unknowingly suck air in under load but never spew a drop. Pesky buggers.

[Meatball]

The float seems to work just fine, although about half the carb diagrams I can find show the needle with a little (spring?) tab as part of the assembly...which if there's supposed to be one, it's definitely not there.

The stock float has a non-adjustable plastic tab molded into it so float height cannot be changed. Maybe the pics you saw of other carbs had an adjustable/bendable tab.

I once had a poorly running Spree and the final culprit was the tiny o-ring on the fuel mixture screw was missing. Sometimes its the smallest things. They’re real sensitive to airbox/filter issues too like simply the lid gasket torn or missing. Worn or stuck reeds, base gasket leaks, etc...these little Honda motors can surprisingly still “run” with a multitude of problems, neglect and disrepair. Albeit very poorly. Keep at it and you’ll eventually find the issue(s).

[motormike]

I can echo Meatballs statements.
"Sometimes it's the smallest things"
"Keep at it and you'll eventually find the issues"
Here's a suggestion to help you diagnose the fuel level in the bowl.
Attach a 12 inch piece of clear fuel line to the bowl drain.
Run the fuel line vertically along-side the carburetor and secure with open end pointing skyward.
The fuel will fill the clear line to the same level that is in the bowl.
You can ride the bike like this and observe what the fuel level is doing in the bowl as it runs.
With the clear line running along-side the bowl, that level is the same in the bowl as it is in the line as liquid will seek it's own level.
This should help you decide if the fuel is being delivered at a sufficient rate.
I noticed you said there was a little bit of gas in the vacuum line.
That is an indication the diaphragm in the petcock is compromised (torn or cracked)
and the very likely culprit in your situation. Fuel cannot be delivered by a bad petcock.

[FredB32]

Back at it a bit this morning -

New bystarter arrived and replaced - didn't change anything.

"Have you checked fuel level in float bowl when it bogs and dies?"
"I noticed you said there was a little bit of gas in the vacuum line.
That is an indication the diaphragm in the petcock is compromised (torn or cracked)
and the very likely culprit in your situation. Fuel cannot be delivered by a bad petcock."

So I did check that the carb bowl HAS fuel in it when it dies. How much I'm not certain. I can release the bottom drain screw and the gas flows out of the carb bowl right when it dies. So fuel is getting from the tank to the carb for sure.

If I give it a little starting fluid, it starts right up and run a little high on idle (2200-2500 rpms) then settles down for a minute or so (or less) and then drops to 500-800 rpms and dies. Giving it any throttle kills it. Leaning towards maybe some sort of vacuum issue somewhere? Reed valve?

"I once had a poorly running Spree and the final culprit was the tiny o-ring on the fuel mixture screw was missing."

I'll double check all the tiny pieces, but from what I recall they're all there. Just went and looked and all the little things seem accounted for...

[Meatball]

Could be fuel delivery issue (petcock)
Could be massive air leak (crank seals, base gasket, etc)
Could be reed petals (unlikely, check this last)

Eliminate those possibilities in that order. Checking the petcock is as easy as pulling both hoses, applying suction to vac hose and seeing if fuel flows from fuel line. Doing this a few times to ensure flow starts and stops when suction is on/off. The vac hose should be bone dry at all times. If theres even a drop in it...the petcock is defective.

The crank seals are simply checked visually (unless you go as far as a crankcase pressure test). To access them, you would need to remove the belt/pulley assembly on one side and the flywheel on the other. Removing the flywheel requires a flywheel removal tool which costs about $5. A leaky crank seal is usually discovered by an obvious sign of oil leakage to that area. In some cases, the seal even pops out and is just laying there. It happened to me once and I just pushed it back in and off I went.

[FredB32]

New petcock ordered. I cleaned/blew out the existing one per the service manual, but I'll pull it and test it anyway to the best of my ability. I'm *hoping* that's what the issue is, and the fuel in the vacuum line is the indicator. I ordered one from Ebay ($10). If that ends up being the fix, then I'll let it go until it fails at some point and look into an OEM one ($50+) if needed.

If that's not the fix I guess I'm investing in a flywheel removal tool. I probably could use one anyway since I've got some other things I'm planning on working on like lawnmowers, etc. that would use it.

I found out last night the belt was replaced recently, and am asking for feedback on the timing of that vs. the issues. Wondering if they maybe mucked up the crank seals doing that job somehow. This will be my first time doing them if needed, but YouTube sure makes it look simple enough

[FredB32]

Well...new petcock arrived yesterday, replaced this morning. No change in issues. Guess it's looking like I need to pull more stuff apart and check the crank seals.

[FredB32]

I've been doing some reading around the forum for a bit. What are the odds it's the battery? I'm going to check it out and test the voltage. Would a bad/weak battery keep it from running? I've seen a couple posts (albeit on the 80cc) that they've experienced similar issues to what I'm having here and replacing the battery seemed to fix the glitch...