puch maxi not starting

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puch maxi not starting

Postby nigel_robbins » Sun Feb 26, 2012 1:47 pm

Hi,
I've recently purchased a 1970 puch maxi but can't get it to start.
The moped had not been started for a number of years.
The plug seems to be wet after trying to start for a while.
There's a spark from the plug when held against the cylinder head.
Fuel flows when I press the carburetta primer button.
Any idea what the problem might be ?
Thanks "
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re: puch maxi not starting

Postby ybot1983 » Sun Oct 13, 2013 12:53 pm

Hello

long time since posting but im having same problem and dont know if you solved it.

Mine did start and run and again has spark and fuel delivery but i noticed that when i take off the clutch compressor to start it makes a phutting noise (likea propeller that doesnt start) as if air is being expelled rather than the low grumbling it used to.

Toby
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re: puch maxi not starting

Postby RebelRider.Mike » Sun Oct 13, 2013 1:27 pm

Neglected mopeds can be hard to start for a number of reasons.
Old fuel, plugged fuel delivery, bad spark plug, bad electrical, low compression.
I'd start by draining the old fuel out of the tank. If you detach the fuel line from the carb end, you can see if the old fuel is getting past the fuel valve ok.
Another thing would be to check for spark. The plug can get fouled by repeated unsuccessful attempts to start the engine. I clean mine off with engine starter fluid. Check the gap and see if you can get a spark with the plug hooked up to the HT wire and grounded to the engine. If you've got spark, give the cylinder a squirt or two of starter fluid and replace the plug.

Now, if its got everything it needs, it should start right up. If it goes a bit and dies, you've likely got carburetor problems. If it doesn't go at all, it might be low compression. If you have a compression tester, 100 psi should be enough to let the engine idle. I've heard 120 psi is normal.

Low compression could be caused by ring, piston, or cylinder deterioration, or a leaky head gasket.

If you can get the engine running but have lousy performance, there could be a leak somewhere. Spraying a little carb cleaner around the carb and intake manifold will show any leaks by changing the idle speed of the engine.

Another thing to check for is plugged exhaust pipe. Oily deposits can build up around restrictions and baffles over time and make the engine work harder just to get the exhaust out.

I've probably missed some things, but that's the kind of stuff I do to keep my Puch running.
Mike

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re: puch maxi not starting

Postby ybot1983 » Sun Oct 13, 2013 3:49 pm

thanks Mike

Ive an idea that my problem may be compression as my Puch was running fine has an MOT till next year, it has a spark against the engine and fuel is fine. I will do a compression check but i think it may be a really big air leak as the sound when i realize the clutch is like air spluttering every time the engine turns over. Ill check the exhaust though as it does drip pure oil and may be so blocked that its pushing the exhaust back into the engine

Toby
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re: puch maxi not starting

Postby RebelRider.Mike » Mon Oct 14, 2013 6:20 pm

There will always be some oil in the exhaust pipe, since not all the oil is burned in the combustion process.

The clutch is in the part of the engine that has transmission oil in it. There is some air in there too, but it should be sealed, and there shouldn't be any air moving back and forth between the clutch area and the crank area.

This is where my experience runs out, (so I may not know what I'm talking about) but it almost sounds like you might have a bad seal. Losing bottom end compression through a bad seal, I think, would cause the engine to get less fuel per stroke that it aught to.

Again, this is a guess on my part. Maybe someone with more experience could give some input...
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re: puch maxi not starting

Postby ybot1983 » Tue Oct 15, 2013 4:00 am

Thanks Mike

I'll check the gasket of the clutch cover. In addition, theres no mention of this in my manual but on the engine where the electrical wires go into the block theres a whole with a plastic tube coming out which i presuime is a breather pipe, however theres another smaller hole facing the front in the space under where the carb goes which has nothing in it. i was wondering whether this should be plugged with something or whether its just a drain hole for water? I attach a picture the hole is at the bottom right just in the side where the engine dipps to fit the carb

Toby
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re: puch maxi not starting

Postby John » Tue Oct 15, 2013 7:18 am

Trans breather hole I do believe on the E50.
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re: puch maxi not starting

Postby RebelRider.Mike » Wed Oct 16, 2013 3:09 am

I just got an empty E50 engine case in the mail.
Image

From what I can tell, there are two holes in the carburetor pocket (or whatever its called). One is for one of the case bolts, and the other is for the cylinder stud. There is another cavity that goes all the way through the engine that looks like it serves a s a drain so water/fuel doesn't collect there.

I think the transmission case vent hole is near the other end of the engine. I can't see the one mounted on my bike; its covered by the frame. But feeling around with my finger, there doesn't seem to be any hose or breather filter on it. Until today, I didn't even know the engine had a breather hole. But it does make sense. Thermal expansion of the oil and air and all that.
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re: puch maxi not starting

Postby ybot1983 » Wed Oct 16, 2013 7:10 am

Thanks for the clarification, i was concerned compression was being lost from this hole. Presumably a bad seal in the clutch housing wont effect starting compression?

Toby
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re: puch maxi not starting

Postby RebelRider.Mike » Thu Oct 17, 2013 1:49 am

There's the clutch cover gasket and the crank seal between the crank area and the clutch transmission area. A leaky cover gasket will just drip a bit of transmission oil. Here's another pic of an old engine case for reference:
Image

The green area is the crank area behind the piston that needs compression.
The red area is for the clutch/transmission parts, and it does not compress.
In fact, it has that breather hole on top for equalizing pressure and venting vapors.

Anyway, if the seal between the crank and the clutch areas is leaky, compression behind the piston will be lost to the clutch area, and could account for the strange sounds coming from the clutch area when the engine turns over.

I'm a noob amateur mechanic though, so it may be something else. I haven't gotten into my clutch and seals yet. I know that the clutch is "wet" as in it is partially submerged in transmission oil so as to reduce wear. Maybe the sound you're hearing is oil sloshing around in there?

I don't know if a bad crank seal would cause an engine to run poorly, or not at all. Also, I'm not sure the seal can be replaced without taking the engine case apart. Might be a good idea to exhaust other less invasive possibilities first, like timing and such.
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re: puch maxi not starting

Postby ybot1983 » Thu Oct 17, 2013 3:48 am

Thanks Mike

Very helpful, im thinking it must be a seal leak, im going to do a compression check this weekend

Toby
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re: puch maxi not starting

Postby ybot1983 » Sat Oct 26, 2013 12:43 pm

i seem to create a new problem each time i work on this bike. I took the exhaust off to mke sure it wasnt clogged with carbon but when putting it back on i manged to clamp the decompressor wire under the exhaust bolts so the clutch handle was too tight and eventually snapped. I retrimmed the clutch cable so it both activated the clutch and decompressor but now the clutch doesnt engage even though it is pulled open and springs back. Im at a loss what the clutch lever on the crank case works i assume it should engage the crank shaft presumably some sort of rod isnt working in the engine

Toby
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re: puch maxi not starting

Postby RebelRider.Mike » Sun Oct 27, 2013 11:31 pm

I'm afraid I'm still ignorant of the clutch side of things. I don't have a decompressor on my engine. And the clutch lever/cable is used on mine only for starting the engine.

Its frustrating to have new issues pop up. When I get stuck, I often walk a way for a while and Google my problems to see what I can find. I often find links to this forum or Moped Army, or You Tube.
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re: puch maxi not starting

Postby ybot1983 » Mon Oct 28, 2013 4:49 am

thanks Mike

The starter handle with a decompressor pulls the clutch and as it moves forward it pulls the decompresor wire that acticates the decompressor under the spark plug. apparently the decomp can be deactivated which i was going to do to see if it was causing a compression problem. It seem very odd that the clutch doesnt engage now even with the decomp engaged or not as it should turn the flywheel. this early model seems to have a very secure clutch cover as well so i might start with taking the clutch lever off.

Toby
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re: puch maxi not starting

Postby ybot1983 » Mon Nov 11, 2013 6:29 am

Dont have much time to work on this bike, but while waiting for a new clutch cable to arraive i thought id check the transmission oil after leaving bike for a couple of weeks. When i unscrewed the oil plug screw nothing came out. So it seems over time it has lost its transmission oil probably from a lose plug. The piston isint seized and turns over, but supposidly no oil in the tranmission i imagine woulndnt allow the clutch to engage to start and may by the source of the whoosing nosie when i tried to start it, rather that the pressure it needed to engage the starter?
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