Tunturi Tiger running problem (Puch 50cc)

Hello, i have a 1984 finnish-made moped that has a puch Vz50N4. It aint running well, like missing all the time and carb settings are probably half a meter off. This "missing" problem has always been on this from the start, when it had a Dellorto Sha 14.12. I bought a 15mm Bing hoping that would fix the problem but it didnt, so to me it sounds like an ignition problem. Spark plug is new, i have tried Bosch, Ngk and champion with the same results. Here's a video:

Re: Tunturi Tiger running problem (Puch 50cc)

♣Slew Foot♣ /

This...

https://www.mopedarmy.com/wiki/Fred%27s_Guide

It prolly an airleak at the carb junction or seals bad rings. Do a compression test and a leakdown. Is there a pinging noise I thought I heard backslap. That would be excessive play in the piston.

Do some of the Fred's and post back.

Re: Tunturi Tiger running problem (Puch 50cc)

The top end has been rebuilded, and i have not driven a single km with the new parts, new piston and bored cylinder. The pinging noise is coming from the exhaust because the sheet metal on it is so thin, but i will look for air leaks now. Compression test result is 9.2 Bar when hot, it has a lowered head. (edited)

Re: Tunturi Tiger running problem (Puch 50cc)

♣Slew Foot♣ /

When they did the top end and mods did they rebuild the bottom end too?

Re: Tunturi Tiger running problem (Puch 50cc)

I mean, i did. I bought the moped and found out that the conrod bottom bearing broke. Took the crank to a old tunturi moped dealer that i know, he still fixes these mopeds up to this day. He changed the bearing and conrod, and i assembled the motor. The cylinder is stock 50mm that the previous owner modded a bit, i had it bored and honed at a local machine shop to 39.5mm and i put a Meteor L-ring piston in. So bottom end and top end are basically brand new.

Re: Tunturi Tiger running problem (Puch 50cc)

♣Slew Foot♣ /

First the simple stuff.

Disconnect killswitch. Run, shut off by choking still does it.

Not a bad switch. Ngk 6hs plug non resistor. Check cap see that it's non resistor. If it is its ok. Just so both aren't resistor type. Fuel flow. Gas cap vent. Prolly not the problem. Does it run right on the stand with the front brake held? If it does it has a bad bulb or a wiring sckowflaw. Magneto feeler foot worn out? Run a ground strap engine to frame. Still do it. Check ht coil coil grounds.

If it has a regulator box grand off of terminal should be away from other grounds. Check resistor in headlight bucket or wiring block. Check the horn circuit. Puch have a weird thing with the horn see bypass under puch in the wiki.

Post back

Re: Tunturi Tiger running problem (Puch 50cc)

Right, thats a lot of stuff to check, thanks.

By the way, what do you mean by "Does it run right on the stand with the front brake held"?

This moped got a manual trans, 4 gears (edited)

Re: Tunturi Tiger running problem (Puch 50cc)

♣Slew Foot♣ /

Run it on the stand with the front brake circuit on. If it doesn't do it it's a safety feature on the ht coil. Preventing it from sparking right like a ground fault in the wiring in frame or fender. Tail might have a resistor or resistor in headlight block might be burnt or grounding. Best bet .

If everything was redone. The thing puts out more volts than normal and the old wiring is rattling and giving an inconsistent spark. Flick the bulbs when checking with a lighting tap like teasing a child.

Run in darkness without the lights on look for arcing. Esp around horn and or bypass.

Re: Tunturi Tiger running problem (Puch 50cc)

♣Slew Foot♣ /

O 1 more thing...

It could be a cracked insulator.

The post where the points are mounted has an isolation sleeve if it's cracked it could cause intermittent anomalies. Also the wire running under the pointset may be bared.

Re: Tunturi Tiger running problem (Puch 50cc)

♣Slew Foot♣ /

Good diagnostic question I forgot to ask rhythmic or intermittent or when I do this...

Re: Tunturi Tiger running problem (Puch 50cc)

Its intermittent, but i will definitely check that!

Re: Tunturi Tiger running problem (Puch 50cc)

♣Slew Foot♣ /

Arc more at higher rpm. So if you rev it and it does it more often or consistently..

Re: Tunturi Tiger running problem (Puch 50cc)

I dont have any wiring done yet, other than spark plug wire to the plug, so i cannot check the arcing

Re: Tunturi Tiger running problem (Puch 50cc)

♣Slew Foot♣ /

Wire it all back. If it's a flaw in the stator you don't have to see the innards yet. You test the components pretty easy.

Re: Tunturi Tiger running problem (Puch 50cc)

Ok.

Re: Tunturi Tiger running problem (Puch 50cc)

♣Slew Foot♣ /

Sometimes I will wire in a multimeter but a battery tester works great.

Re: Tunturi Tiger running problem (Puch 50cc)

Right, was wondering how do i check the inner components with a multimeter to see if they are o.k?

Re: Tunturi Tiger running problem (Puch 50cc)

♣Slew Foot♣ /

You got volts out. So it's not a coil. It's intermitant not cyclic.

Re: Tunturi Tiger running problem (Puch 50cc)

♣Slew Foot♣ /

Rule out bad coils bad ht.

Out go switches so we 're left with electrical gremlins. Or a worn pointset.

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