I'm starting to hate my 'ped.

david f martin /

Back again. I've been keeping you posted, so here's the latest. Saturday, I tried running some 2-stroke oil in the gas, thinking that maybe the oil injection pump wasn't putting out. I wound up having to limp back home and took the half day off from work. I dumped the gas, put some fresh in, couldn't test drive it because of the rain. Yesterday, I had to watch my sister's kids, so I didn't get a chance to work on it.

I drove it to work this morning, and had to help it up the worst hill on the way. Took a 2 hour lunch to work on it...

Completely disassembled the carb, cleaned it inside and out, put an inline fuel filter on it, reinstalled (with stock jet)... Still ran like shit. Ok, maybe I need to try to get it closer to stock, as much as possible...

Covered all the holes in the aircleaner I'd drilled previously. Found a restricter for the pipe that was only slightly bigger than the original tailpipe. Pulled the cylinder head, cleaned it and the top of the piston with a soft brass bristled brush till they looked like new. Set the plug gap on the high end of spec. Checked the compression with my fingertip...

On the way home, I had to push it up a hill. It was getting dark, it was windy and cold, during the tail end of rush hour traffic. I wound up pulling over, took the restricter out of the tailpipe, pulled the aircleaner (completely), and practically dragged it home. I pushed it hard down the hills, almost hoping it would just self-destruct, the little bike making deafening popping noises as it 4-cycled thru the straight pipe. Going up the hills, I had to push it along as I cursed it loudly...

Before you jump to conclusions about me, you should know that I am used to working on temperamental antique machines (in fact, this 17 year old bike is the newest machine I own). I don't get mad when I'm working underneath an old VW, and a piece of 30 year old crud falls into my eyes. I'm used to busted knuckles and rusty bolts and things falling apart. I just take it all in stride. In fact, I'm one of those few mechanics who rarely ever curse (and usually when I do, it is quietly at myself for overlooking the obvious, not at the machine).

I put a lot of love into this machine. I've decorated her with jewelry and surplus army gear, bought her lots of new parts, bought the shop manual, taken time off from work to fix her up, patiently fixed flat tires (once in the rain, even), brushed aside jokes and snide remarks about her in good humor.

Now I'm starting to lose the love.

My only remaining idea (and I feel like I'm groping in the dark here) is that my battery is weak (maybe dead). I thought that the magneto alone powered the ignition, and the battery condition was unrelated to how the bike runs, but now I'm wondering if maybe it is the reason I can't get any RPMs out of it... Not enough juice to produce a spark fast enough?...

I could use a few wise words from you gurus...


Re: I'm starting to hate my 'ped.

i can't help you here ... but just to encourage you to not lose hope! i think some of the gurus will probably be of help soon enough.

be sure you give specific info on everything involved w/ your bike. one question i have, though, from my own experience. when you say it runs horribly, do you mean really slow? or unreliably?

you might need a larger manifold hole in the piston cyliner if you're just terribly terribly slow. my bianchi 1977 had an incredibly small hole and that was the main problem. oh, and a larger carburator helpd a bit, too. but it was the manifold hole ... an absolute restrictor and kept me around 10mph (not enough power to go up hills).

let me check the rest of your posts to see if i can think of anything else ...

simply your mechanic approach


i just read your past posts ... and i'm a bit worried that you might be damaging your ped. please bear w/ me, i mean no disrespect.

the hacking off the muffler, will lead you to trouble. so might the drilling out of the jet.

i think ree and ron and the others had it right to take the repair thing slower. here's my advice (mind you, i'm not an expert at all and i'm only familiar w/ a minarelli engine).

the best place to start a repair is w/ the carburator, as others suggested. take it off, and clean it. don't mess w/ drilling jets unless some told you to. everyone tells me it's such a bad idea. besides, you don't really need a bigger jet ... my ped runs faster w/ a 49 than w/ a 62.5. so go figure. most people in the moped army prefer 52 or thereabouts. i'm using a 55, but will switch to a 52 soon, since it'll give me more top speed (i'm pretty sure of that).

so clean the carburator thoroughly. check the float, it might not be a tight seal. also, check the petcock to be sure plenty of fuel is going in (also be sure your inline fuel filter is clean; put one on if you don't have one). doing those things takes me about 15-20 mins tops and usually solves the problem.

if that doesn't fix it, then you move on to tougher things. if the moped starts and all (as i think you imply), then it's not really an engine problem (please someone correct me if i'm wrong here). that means it's probably a fuel problem or something like that. check your idle and throttlw settings in general, that sometimes helps a bit.

if it ran well before ... and i think you mentioned that it did, then just a regular maintenance check should do it. do the simple things first, one at a time, then move on up to harder things. don't do anything drastic until you check w/ the gurus first. from everything i've been told (and warned about), the 2-stroke engine is completely different from anything else. so don't assume your experience (which is, no doubt, quite extensive) will translate easily into this.

my brother is an engineer and designs parts for cars (some of his stuff is on the road and in concept cars at this year's auto show). he knows his way around cars; he rebuilt a camaro when he was 15 for his first car and has been moving up since. he was baffled by my 2-stroke minarelli engine. in terms of general theories of propulstion and such, he can figure it out. but in terms of what to do to fix it ... he left that up to me completely. so, go figure, eh?

anyhow, that's all i can offer you. sorry i can't be of more help.

oh, wait, i do know of something you could've tried for the muffler. here in kalamazoo, we take them off (unsrew, not cut!) and set them on fire. it cleans the carbon out of them really nicely. then we put them back on. if you need a muffler, check on ebay or put in a request on the for sale forum. you might get lucky.

good luck w/ the repair work. don't give up on the moped! you can also try talking to it. my "lucia" seems to do better when i woo her in italian. ;-)

Re: simply your mechanic approach

Sorry to hear about all the problems, I am a older auto mechanic and found out like yourself you can look to hard to find a problem, I once put a timing chain in a Mustang and only to find it needed a condensor! that was only a week old ! The car would not rev-up and backfire....Sound Familar? Also found a coil wire to do the same....may be worth taking a closer look....GOOD LUCK DOUG

Re: I'm starting to hate my 'ped.

First of all... You should tell us which ped it is. What year?. Mileage?

(but as I remember it it is a Euro... so I am not an expert on them)

And I am glad you are a wrench for a living.

And I am almost surprised that you need help.

But..... here goes.

I have never seen a small engine that has to have a fully charged battery to run.

On most of them the battery really only has 3 functions...

1st... as a large voltage regulator (and that is whether it is alive or dead) to keep light bulbs from blowing at high revs.

2nd... to keep the lights from going too dim at idle speeds at night.

3rd... to spin the electric start (if it has one)

So I can say you can rule out the battery as a source of trouble (dead or alive).

You said the oil pump might be on the fritz... bad news.

Why do you say this?

Has the oil level stayed the same for months?...bad news.

But they don't drink a whole lot of oil either.

But if the oil system failed a month ago... no amount of oil will now "fix it".

You say you removed the head and scraped off carbon... OK....

But did you push the piston to BDC and look (with GOOD light) for scoring and scuffing down in the cylinder?

You could have ruined the ring seal by starving it for oil without getting an actual seizure.

If this is a ped with the exposed head and cylinder.... pull the cylinder right off (easy as can be) and take a close look at the piston skirt and look for heavy scuffing... and even aluminum from the piston smeared over the rings.

If that is the case you need an oversize piston and rings and a bore job.

And toss the oil pump and premix it.

Also... put the piston in the cylinder and stick a feeler guage in between them (the piston should be in the BDC position while you do this measurement)....What is the clearance?

Also... You said you cleaned the carb... That means you used 100 psi of compressed air thru all orifices many times?

While you have the cylinder off play with the rod and look for evidence that the rod bearing or crank bearings are gone.

Push it, pull it, spin it... you are looking for too much friction, stiff spots, funky noises, too much play.

You of course have the proper spark plug?

Re: simply your mechanic approach

Doug D. beat me to it.

A bad condenser will cause the problems you describe, particularly after it warms up. I once replaced th points on my truck during a tune up and found it ran worse than before. Long and short of it: replaced the "new" condenser with the old and everything was fine. Took the bad one back to the auto parts store and they said they didn't exchange electrical parts.

Jim C.

Re: simply your mechanic approach

david f martin /

Thanks, Miguel.

The bike has been running poorly for the past few days, and all the steps I've been taking have been attempts to get it going again.

I've got 2 jets, one that I drilled out and one that is stock. I'm running the stock one right now. The carb is clean inside and out, and I'm running an inline fuel filter. The plug is what the book specifies, and gapped within spec. I check the condition of the plug every time I've tried making adjustments, just to make sure I'm not running too rich or too lean.

Cutting off the stock muffler was an act of desparation, as I could not think of another reason why my bike was running so poorly. A fellow 'pedder has a used Tomos biturbo I'll probably buy from him, so I can get rid of this noisy straight pipe...

I have a fixed CDI ignition, and I don't really want to mess with that until it is a last resort.

If my bike were just a toy, I could be a lot more patient with it, but it is my only transportation right now. My trip to work is 11 miles one way with lots of hills on a 6 lane with 50mph traffic. That's why I'm getting so frustrated...

I'm not trying to hotrod the thing, I'm just trying to get it to run as well as it did when I got it.

When I flip the ignition switch to "Start", the light doesn't light anymore, so the battery is obviously dead, and is running strictly from the magneto. That is the only thing that I've noticed that coincides with the way the bike is running, which is why it is suspect...


Re: I'm starting to hate my 'ped.

david f martin /

Hey Fred,

It's an '84 Yamaha QT50 (Yamahopper), with about 4k miles on it. I don't really have a reason to suspect the oil pump, other than that I've already covered the most obvious bases... I'm running the plug that the book calls for, gapped within spec. I pulled the head, but not the cylinder. I guess that's my next step. I'm pretty sure there is no dirt in the carb (right after I've cleaned it thoroughly), and I now have an inline fuel filter in front of it.

The bike won't rev up like it should. I can't get enough revs to engage the clutch properly. It is topping out way below where it should, before it starts 4-cycling. The plug looks ok, I don't think I'm running too rich, but a smaller jet is definitely on my shopping list.

The way I figure it, since nothing I've done so far has made an obvious improvement, I haven't yet found the problem...


Re: simply your mechanic approach

Hey David, was just thinking, allong with other ideas, mabe ? the flywheel key could of sheered? Just another thought...Doug D.

Re: I'm starting to hate my 'ped.

Does this bike have a reed valve ( a one way "flapper" valve) ?

It is in the intake between the carb and cylinder.

You can tell if it is functioning correctly by putting it up to your mouth and sucking on it... it it barely flows... it is good.

How about carbon plugging up the exhaust port of the cylinder?

Rear wheel spins freely when the ped is shut off?

This would be the first one I've seen that needs a good battery to run.

But the fact that the light on the dash quit when it started running bad might be a clue.

Meant to ask

What is the spark plug color during all this?

Re: Meant to ask

oh, it's one of those japanese mopeds ... i think i remember being told that they do need battery (if they have a cdi ignition). hurray for the battery-less minarelli engine ...

sorry you're having so much trouble, dave. that's really horrible. i hope you get up and running fast soon. but it's obvious that there are now tons of people trying to help. that's why i love this forum and moped life in general ...

make sure you let us know how it all turns out ... so that we can tell others if similar things happen.

Re: I'm starting to hate my 'ped.

Ron Brown /


I go out for a beer and you fall apart!

I just finished reading this thread. It took a while!

I'm with You and Fred, I think you may have an ignition problem. You should try to find out if the battery has anything to do with the ignition before you beat yourself to death over that one. It could be a bad cdi unit if it does not require a battery.

Keep a couple of things in mind as you work:

The Mantra:

It's only an engine...

It's only an engine...

The problem:

Two cycle motors are so simple that when they do not run correctly, it is really difficult to find something to fix. Never assume anything is good, just because you just replaced, cleaned or repaired it. When you have a problem, try one thing at a time and immediately return it to the way it was, before moving on to the next potential solution (don't put the dirt back in the carb).

After you have tried everything and failed, the thing you did not try is the problem. In this case it sounds like the cdi or battery, but never overlook the spark plug, wire and cap.

Oh, and never give up. It's only an engine... It's only an engine..

Remember, in the words of the immortal Red Green, "We're all in this together"


Re: I'm starting to hate my 'ped.

Reeperette /

I will wait till that cylinder comes off, for my diagnoses.

It really sounds like one has a handle on the problem, if one can just figure out what the flamin hell the problem IS, exactly....

Another out of the blue thought could be worn clutch plates, but lets not go there till we check the simpler stuff.


Re: I'm starting to hate my 'ped.

david f martin /

Thanks, fellas. I'm glad I'm not all alone in this...

One of my co-workers, Wayne, took me to the cycle shop at lunchtime today, and I bought a battery and had them put it on a trickle charge overnight. Wayne admired one of the bikes there (a 650cc single cylinder Suzuki), and we wound up being held hostage by a couple of salesmen out front, where the bikes were. I love cycles myself, but I'd forgotten to bring my coat with me and damn was it cold and windy out there... (Yeah, I'll take some cheese with my whine)...

Anyway, I'll have a new battery tomorrow and hopefully that will fix it. Wayne gave me a coil he'd bought for his long gone Tomos, but I don't know if it would work with my ignition system. If I can just get it running half as well as it should, I'm considering a biturbo and maybe some new rings...

I'll keep y'all posted...


Get a Divorce !

The honeymoon is over

Re:Give it a enema and aspirin


Re:Give it a enema and aspirin

Ron Brown /


Should he call you in the morning?


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