Suzuki A100 power loss

[foamy]

I've got a mint little 92 A100 that has been running perfectly until last weekend. On the Saturday it was running fine and after a blat I put it away, jumped on it on the sunday and straight from start-up it had no top end or power under load. Basically idles fine and starts first or second kick as usual still. I have checked the carburettor out, no sticking float and very clean. Fuel supply to the carb flows fine. I changed the spark plug just in case and the exhaust is unclogged. I can start the bike and fully open the throttle in neutral because the motor just won't rev like it used to. Whatever it is it's sort've like some component died instantly on start-up, could a condensor do this?

Thanks in advance for any help.

[YellowDog]

De-coke it.

[foamy]

De-coke what? The muffler is clear. Is there something else that can be de-coked?

[YellowDog]

De-coke what? The muffler is clear. Is there something else that can be de-coked?

It's the cylinder head that gets coaked up; especially around the valves.

I'd check the compression before doing anything else. If you had a good blast, maybe your piston ring is not now too clever.

You've put in a new plug and adjusted the gap, what about the contact breaker points?

[foamy]

I took the magneto flywheel off to have a better look at the points etc. The little fibre block on the points looked worn and the cam on the boss of the magneto flywheel was dry because the oil wick that is meant to provide the lube had long dried up, the points still open with a clearly visible gap and look clean. I discounted anything being out of tune because surely this would deteriorate slowly, not fine one day and crap the next. I took the exhaust off at the head, there was sooty carbon there. But once again wouldn't this be a gradual loss of power? Checked the compression and if I remember correctly it was up around 100psi, blew the gauge out though even when held firmly. The kick starter also feels firm and kicks back occasionally.

Thanks for your interest so far, I have been in engineering all my working life but two-strokes are not my strong point.

[YellowDog]

I can see you are on the ball. I am just thinking back to the early 80s when I had a Suzuki GP100. I had a serious loss of power however liek you say, it was a gradual loss until one day it wouldn't manage 3000rpm in neutral. After the de-coake, it was like a new bike. Potentially, your blast of power could have loosened the carbon depositis however I am now thinking about carb jets or the diaphram.

Good luck.

[RDjase]

It mite have a double skined exhaust and the inner pipe has colapsed and blocking the exhaust (old hondas did that from memory) , or maybe a crank seal,
seems strange it was running good and then suddenly played up tho,

[foamy]

Yeah bloody annoying really, I dismantled the exhaust completely, just a thin carbon coating on everything but otherwise mint. If it was a four stroke its as if the advance has stopped working. How does the spark advance work on a two stroke? I was expecting to see some sort of mechanical advance set-up inside the magneto flywheel but zilch there. I will put a new condensor in and anticipating that it will not solve it I will take it to a shop. Can anyone recommend a good repair shop on the shore? Should I take it to a mower and chainsaw repairer (joking hopefully).

YellowDog: To de-coke do you remove the head, piston and cylinder and just wash them out? The carburettor honestly looks like it came out of the factory yesterday, the diaphram theory is interesting mate, it would be getting on to 17 years old now. The bike has 14,000km's on it. Suppose its still a fair mileage for a two stroke.
Cheers guys, appreciate the input. Will have a think over your suggestions.

[YellowDog]

The Honda boys are on Barry's Point Road.

A de-coake is always a good idea anyway. Yes, just take the head off and scrape all the black stuff off. Try and leave it sandblaster clean, thought my Mickey Mouse (successful) attempts have been performed with the end of a metal file and sandpaper. There's a product called SeaFoam, that softens it up and leaves it looking like new.

You'll just need to get a new gasket. You don't need to touch the piston, though whilst the heads off and depending upon the number of Ks, a new piston ring won't do any harm.

There have been a couple of threads on here where such problems have been remedied by taking it all apart and then putting it back together again however I am sure you would rather find the actual problem.

Good luck.

[SS90]

Don't worry about the diaphragm suggestion (would be a logical one if 2 strokes used diaphragm carbs..... they don't, they just have a round slide returned by a spring, so no drama's there.)

17,000KM's is absolutely nothing on one of those, and I would first suspect the condensor/ points.

Just the way the problem appeared points in the direction of a condensor. Opposed to, like you say carbon deposits etc.

I also would suspect the main jet, but if you have inspected all that, then it is unlikely.

I don't personally see the need to decoke it (oils have come a very long way in the last 20 years, and it is less of a problem than before (unless you are using lawn mower oil or something silly)

If you can readily get a new set of points/condensor, that would be my first point of call!

[foamy]

SS90
I have removed the condenser and today tested it like you are apparently meant to, I placed a megger on it and charged it up but it stopped on 10megohms instead of carrying on like it should. Also it wouldn't discharge with a spark like it is meant too. Getting one could be an issue, it is an original item with the little bracket attached that holds the oil soaked piece of felt to lubricate the points fibre block. Colemans Suzuki maybe?

Thanks for the advice on the diaphram, I realised this morning that there wasn't one because I had the carby apart yesterday.

One question: Can a dodgy condenser still allow the bike to start and idle ok but have no guts, suppose I'm going to find out. Thanks for your help.

[quickbuck]

One question: Can a dodgy condenser still allow the bike to start and idle ok but have no guts, suppose I'm going to find out. Thanks for your help.

Well, the function of the condenser it to prevent arching of spark across the points....
The function of the points is to collapse the coil that gives your high energy spark....

NOW, if the points weren't able to "Break Contact" in a positive manner, then the coil will not collapse in a timely manner...

So, I would say YES!
A dodgy condenser could produce the symptoms you are experiencing....

Somebody please correct me if I'm wrong...

[Pussy]

Well, the function of the condenser it to prevent arching of spark across the points....
The function of the points is to collapse the coil that gives your high energy spark....

NOW, if the points weren't able to "Break Contact" in a positive manner, then the coil will not collapse in a timely manner...

So, I would say YES!
A dodgy condenser could produce the symptoms you are experiencing....

Somebody please correct me if I'm wrong...

I reckon you and SS90 are on to it

[SS90]

Yea, I think we are all in agreement here,

I think the fault is the condensor, and really, if you can't get the correct one easily, just go to Repco, and find one close enough.....

Condensors are categorised by "MICROFARIDS", and at the end of the day, it is not a big issue to have one that is not "100% in spec"

I used one from a Leyland Mini on a Moto Guzzi once....worked perfectly!


The points may be a different issue though....and just because you can't see "errosion damage" doesn't meant it isn't so..........

Faulty condensors cause damaged points, so always replace as a set to save drama's!

[YellowDog]

Yea, I think we are all in agreement here,

I think the fault is the condensor, and really, if you can't get the correct one easily, just go to Repco, and find one close enough.....

Condensors are categorised by "MICROFARIDS", and at the end of the day, it is not a big issue to have one that is not "100% in spec"

I used one from a Leyland Mini on a Moto Guzzi once....worked perfectly!


The points may be a different issue though....and just because you can't see "errosion damage" doesn't meant it isn't so..........

Faulty condensors cause damaged points, so always replace as a set to save drama's!

I do like were this is going.

All I would say is that my experience with condenser/points problems is that they usually show themelves in the starting/idling phase. This motor idles just fine implying the gap is opening and closing as it should.

I hope this is the problem. The only other thing that I can think of causing this problem is the timing becoming seriously retarded. I guess a condenser/points problem could well have this effect.

Will be interested to see how this one concludes.