Forum

[simon]

Id be surprised if it was the mag. Generally it will give other signs of weakness than just dificulty starting warm, missing and fouling plugs etc. with the monobloc you should check that you have the right idle circut jet in as a rich one will be always wrong at some pojnt. stuggled with this for ages with my bike when I fitted the 389. Once I got the jet right it was a doddle to tune on the air screw and would idle warm or cold. You can can take the cover nut off the jet and attach a length of clear pipe to the bottom of the jet that when held next to the float bowl will give you the float height. It should align with the little nipple in the middle of the float chamber cover. If you knowmsomeone with a megger they can check the continuity of the coil if you want to check the mag, if the magnet was weak it wouldnt chuck a decent spark hot or cold but whatever I certainly wouldn't swap an SR1 for a battery and coil.

[simon]

Also re reading your post it does sound like a venting hot carb. Next time you stop for a bit and it wont start try kicking it over a few times with the trottle wide open and the decompression lever pulled. You might find that this clears the rich fug and it starts.

[Chris Tindal]

Hi Dennis

It does seem to have made a difference but it may have just been a fluke yesterday. I think I need to check all the jets with my data sheet for Redditch bikes. Thanks for your input Simon, I dont intend to ditch the mag and will persevere. I was left stranded last weekend when it got hot and sulked and even the full throttle technique didn't work. I think the next job then is to get the jets out.

[Revband]

Well as is to be expected on a message board everyone has an opinion, If I were a gambler I would put money on it being the Magneto, I have been servicing and repairing them for more years than I care to remember and think dennisc has got it spot on, the magnetic rotor on any SR Magneto will by now be getting weak even if the rotor has never been removed from the body, you can almost guarantee that it has been removed and the longer it spends outside the body the weaker the magnets get, and as dennisc said they become even weaker when hot.

One thing to check on the SR as well, if the cam has been removed it may have been refitted slightly of the point of maximum flux which also weakens the spark, details to reset the cam can be found on the Brightspark web site.

[Chris Tindal]

Thanks Revband, I'll take a look.

[Chris Tindal]

After a good day Thursday, it seems to have been a fluke. Yesterday it went back to its symptoms of poor starting, not just when hot, bit intermittent when cold. Today I stripped the carb - Mark M - all the jets are bang on for a Bighead with no filter. The manual says needle position 3 so altered it to this and kicked it over. It started but soon stalled and wouldn't start again. PeteF - checked the float height, it seems ok although it was by eye. WDCO42 - there was already a Tufnell spacer and two gaskets between the head and the carb so I'm happy with that. Tim NZ - took the plug out, it's a new plug on the factory gap, reduced the gap and put it back. It then started and ticked over, so helmet on and off round the block. With the needle in position 3 it pulls like a steam train and is really smooth and tractable. It has started again repeatedly all afternoon. So with the carb set up well I think it's the plug gap that's made starting easier. DennisC, Rattlebattle and Revband, I think your right about the mag! Looks like it will have to come off and get serviced over winter. Thanks everyone for their help

[Chris Tindal]

Simon, I agree, despite the agro I'm persevering with the mag.

[Dennis C]

Chris, I was speaking from hard earned experience, I went round in circles trying many different things, every time I thought that's it cured, but after a few weeks back to bad starting again, remagnetised the armature a couple of years ago and been an easy starter ever since, also a couple of friends with the same problem have now had their bad starting cured in the same way.

[Chris Tindal]

Anywhere you recommend Dennis?

[Dennis C]

Everyone seems to have a preference and some people have had a bad experience where others sing praise with the same people, if you just want the armature remagnetised it is probably best to see if you have anyone fairly local to take it to, they may do it while you wait?, If taking the bare armature you can wrap a length of old chain round it as a keeper, my last one was done by Armoto in Chesterfield.