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Jcm 240 Starting Problem


bigplonker
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Help!

I bought a 240 JCM trials bike some time ago which appeared to work perfectly. However, I've since discovered that when the engine is hot, she's difficult, nay impossible, to start. Then when the engine cools down, she starts perfectly again. I suspect that it could be a problem with the little red box thing under the petrol tank which I think is something to do with electronic ignition perhaps??? I've thrashed her with a leafy branch, called her a few unprintable names and locked her away in solitary confinement for a few months but she still flatly refuses to behave. Any technical advice would be much appreciated.

http://s605.photobucket.com/albums/tt136/b...nt=P1000738.jpg

Edited by bigplonker
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Help!

I bought a 240 JCM trials bike some time ago which appeared to work perfectly. However, I've since discovered that when the engine is hot, she's difficult, nay impossible, to start. Then when the engine cools down, she starts perfectly again. I suspect that it could be a problem with the little red box thing under the petrol tank which I think is something to do with electronic ignition perhaps??? I've thrashed her with a leafy branch, called her a few unprintable names and locked her away in solitary confinement for a few months but she still flatly refuses to behave. Any technical advice would be much appreciated.

Stick with percussive maintenance, works for me !

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Baldilocks - thanks for the offer of further info if required. Very kind. Firstly though, I'll try my hi-tech solution of bashing the mysterious red box thing under the tank with an axe and see how it goes. Failing that, I've emailed 'Trail70' out here in France (Joel Corroy's bike shop - he of JCM initials who originated the brand) to see if they can offer advice, but as my French is appalling they probably won't have understood a word of my message. Ho-hum.

Interesting that you did the SSDT on one of these. I presume it got you round okay, despite your mention of weak sparks at low revs. Haven't noticed that problem with this particular bike. Mind you, I've only ridden her for about five minutes. Incidentally, the rear shock seems fine and the engine's sweet as a nut. According to the previous owner (in Cumbria) the bike's never been trialed, just trailed a bit by him and the first owner (a lady). Lack of scratches on bashplate etc. seem to confirm his story. Strangely, he never mentioned the hot-starting problem!

Anyway, yes, it would be nice to get her running right again. Sadly, I know little about electrics though (which I presume is the cause of the problem).

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In those days we didnt used to run a tickover, ideally I used to set my bikes to run about 5 beats before stalling.

you couldnt do that with that model JCM, if you left the tickover the same sometimes it would stall almost instantly sometimes 5 beats. Doesnt seem that important but when riding it was very difficult to gauge when it was about to stall.

Problems at the SSDT were mainly the shock losing its damping due to the shim stack breaking up then bursting the rubber diaphram which held the oil. The major plus was the air filter system, that year it absolutely lashed it down but you couldnt drown a JCM, the air intake was up by the HT coil, a cracking idea.

when re fitting the rear wheel always remember to connect the rear brake cable. Some people have been known to forget to do this and then crash into the SSDT time control hut in the car park..... :rolleyes:

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There are some JCM parts of ebay UK at the moment including a Motoplat stator.

The guy has done an odd thing though and listed the upper and lower crankcases as separate items! Hope if they sell they go to the same person :rolleyes: Being machined as pairs n all!

Still wonder why more manufacturers don't do horizontally split cases.

Wayne...

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  • 4 weeks later...

More advice please!

The hot starting problem continues (no problem when engine is cool).

Following on from my recent similarly titled posting...

I duly purchased the second-hand JCM Motoplat red box coil thingy advertised on eBay (thanks to the person who alerted me - sorry, forgotten name). Arrived in the post yesterday. Attempted to fit it this afternoon and, as usual, failed miserably. Problem seems to be that the 'red box electric thingy' (my description) that's currently fitted under the petrol tank is somewhat different to the 'new' Motoplat one.

The currently fitted one is box-shaped, doesn't have a brand name, has two male prongs (one large, one small - same as Motoplat item) plus an HT lead and a small 'built in' wire which earths (I presume) onto one of the two bolts that hold/connect the unit to the frame.

The Motoplat item is cylindrical, bigger (when fitted, there's no space to get the plug cap on or off), has an HT lead and the two male prongs that fit into the female connectors, but instead of having the small 'built-in' earth(?) wire (as on the 'old' unit), it has a separate 'thickish' wire with a 'washer-type' connector at either end (one end presumably earths to frame and the other end presumably somehow connects to..., er..., dunno for sure but maybe the Motoplat unit????).

I've taken a photo of both units side by side which I'll attempt to load, soon as I can, onto this Photobucket wotsit that I recently joined.

My questions are typical of a gormless idiot with no mechanical knowledge whatsoever and even less knowledge about 'sparks'...

1) Is the Motoplat unit completely wrong for my JCM even though it apparently came from another JCM, albeit maybe a different model?

2) If I fit the Motoplat unit but without connecting the thicker earth(?) wire supplied, will I (and the bike, and perhaps the whole village) disappear in a puff of blue smoke the moment I kick-start the engine?

3) Have I ruined the existing unit by prising a side panel off and peering inside (curiosity y'know) to be confronted by what appeared to be a solid mass of black plastic and nothing else (surprisingly, no wires or cogs or weird little electrical thingys)?

4) Is there anywhere I could send the existing little red box thingy to get it repaired (if indeed it's malfunctioning)? (I believe someone kindly suggested earlier that Bradford Windings - or some similar name - don't have previous posting in front of me at the moment - might be able to help.)

5) Could the cause of my hot starting problem be something else entirely?

6) As the existing unit isn't a Motoplat item, what is it and where could I source another? (Have emailed the JCM's birthplace for advice but didn't understand their response due to not concentrating hard enough in French lessons at school. I think they were on about a solution costing 400 euros - about 380 quid. Pardon?)

As before, any advice would be much appreciated.

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