Pw50

[enrico]

Hi all,

I realise that this is not strictly trials related, but if I get it resolved then we may have another member of the trials riding fraternity!!

I have acquired a PW50 which is old but essentially in pretty good nick. It was left standing for some time and no longer runs.

I have flushed the tank, cleaned out the carb - which had filled with 'varnish' like old petrol deposits. Jets were partially obscured but have cleaned and blown through and all appear ok now.

Electrics - there appears to be a spark but not a big fat one. Does anyone have any info on testing the electrics / coils on these things? Having 'googled' the issue I have tried disconecting the handlebar switch - but to be honest the spark is still pretty much the same. Have fitted a new plug.

The bike still wont start - doesn't even fire - but strangely the plug doesn't appear to be getting wet. Do these bikes (late 80's vintage? Red and white) have reed valves? If so presumably they are in the carb manifold where it abuts the cylinder - which looks to be a pig to get at/out?

Any ideas or help gratefully received as I have a little person busting my a**e as to when their bike will be running, and I'm too old to keep pushing it (and them) around the garden making motorbike noises as I push them!!

Thanks!

[twinshockdude]

sounds like new crank seals needed.

[enrico]

Thanks for the idea, any way of testing them?

Update from tonights attempt - have removed and cleaned the reed valve - and the carb again. Reassembled without air filter or exhaust.

After a few kicks it fired and then ran (noisily without the exhaust) and as I had disconnected the run/start/stop switch I turned off the petrol and ran it until it ran out.

Feeling very smug with myself, I put the exhaust and electrics back on, but having done that it then wouldn't fire or start - grrrrr. So, I removed them again and now it still wont even fire? Could it be due to a weak spark that will give enough to run once started but not to start (easily)??

There appears a strongish spark at the ht lead, but not so strong once the plug and cap are fitted (both new).

Anyone have any idea on how I can test the coils/electrics - presumably there should be a resistance figure that I could check for on the coils and the other electrical bits before I throw the damn thing across the workshop!

Edited July 31, 2008 by Enrico

[ar22]

had one of these until very recently

mine was also a nightmare to start and then would not rev out

I tried all the things you have and more

in the end I took the barrel off (5 minute job) and found the exhaust port at the piston very coked up, 10 minutes gouging with a screwdriver let the biggest amount of rubbish I have ever seen out.

new head gasket and bike started 2nd kick and could pull me (19 stone) admirably round the garden

make sure the collector box is not blocked (you may need to cut the back out of it)

these wee bikes are bullit proof and the best starter bike by miles, don't give up

there is a dedicated pw site where I feel you may have a better audience and some very knowledgable pw owners who have seen everything and more

http://pwonly.com

[enrico]

Excellent - thanks for that. There will be two very happy people if I can get it going - and one of them will be my daughter!!

[paulthistle]

Enrico,

I have been working on PW50's since 81.

The engines are virtually the same since inception. The pwonly.com site sells parts off of the chinese copy of a PW.

If you have cleaned the carb and tank, also clean the fuel screen in the "IN" side of the fuel valve. It is plastic, you can screw a tap or woodscrew into it and pull it out to clean it.

The right handlebar switch has a plastic multipin connector under the front numberplate. If you unplug it, you can start the bike in the run position. The start safety feature will be disabled.

The spark plug cap has a resistor in it, it should be between 5K and 10K ohms. Use a BPR4HS NGK plug.

If the exahust port is clogged, the pipe will also be clogged. You can try running it with the pipe loose and the gasket out.

Hope this helps,

Paul

paulthistle@hotmail.com If you still have questions.

[enrico]

Cheers Paul,

Off on two weeks hols tonight - so it will sit in the workshop until we get back (at least I hope it will still be there when we get back!!).

Will follow up your recommendations when I return, and thanks for the info.

Eric

[kevin j]

I had one years ago for daughter.

Mine also had a Start/run switch that affected the timing. Must be in the start position, and would not rev up in that mode, thus could not start with WOT and cause the centrifugal clutch to engage and take off. Then, once running, it would die if throttle applied. Must move switch to Run, then it would accelerate and go.

also had an exhaust restictor that plugged up, so tossed that.

Just FWIW, the rear ring gear from a scooter QT50 is bigger (scooters were like PW drivetrain but bigger wheels, hence geared lower.) and gears the PW down better for slower speed and better torque/off road lugging. The scooter also had only one sided support bearing on rear axle. The axles were shorter, so could not just exchange the assembly. I just prssed out the axles and pressed the ring gear onto the PW axle and put it back, The pinion stays the same. In theory, gear mesh is slightly off, but these are just bevel gears, and they will still last forever. It wa s good modification for using the PW in trials youth situations.

k