Lack of engine power

[Felters]

Was out testing my new SRM clutch yesterday when the bike suddenly seemed down on power. It would rev ok in neutral but I was struggling to get the bike over about 45mph in any gear. I'd just filled the tank - although it only took about a gallon - and as soon as I got home I whacked a new pair of plugs in. Made no difference.

I've got a feeling it's probably the carb - the magneto has just been rebuilt and it normally starts first time so I'd be surprised if it was electrical. Any bright ideas?

PS The SRM clutch pressure plate is a "good thing".

[t20racerman]

If it packed up straight after you filled up I'd check your fuel for contamination. You can get water at the very bottom of a fuel pump tank. Drain the float bowl and see what is in there.
Also, what are your plugs like?

[Felters]

The plugs I pulled out looked ok - if the temp get's up a bit this week I will give the carb a severe looking at.

[wilko]

Timing slipped?

[bsa-bill]

Clutch slipping ??

[orabanda]

Compression test would be useful (and easy)

[chaterlea25]

Hi
If the tank was 3/4 full and the ""fuel"" has been standing for more than a month or so, its gone off
the gallon you added wont help much
Drain the tank and start with some fresh fuel
HTH
John O R

[orabanda]

Wilko makes a good point (pun intended) about timing having changed.
Check points gap; should be between 0.012" - 0.015".
If the adjustment nut(s) work loose, the gap and timing will change, and the performance will change quite suddenly, and suffer.
I have had this happen. I now always include a set spanner in the tool kit which matches the nuts (from memory; 1/4" AF) because it is difficult to re-adjust points by the side of the road, without the right tool!

Also, the bakelite heel which follows the cam profile can also wear, with the same result.

Richard

[beezermacc]

Hi Mike. I've sent you a pm. Give me a ring if you need any help.

[andy2565]

process of elimination,plugs points timing carb,tank filter,compression,of which i use a leakdown test rig which is better,good luck,it sounds like the mag,but best work your way down the list.

[Felters]

Well who knows? I closed the points slightly to get them to 12 thou, made sure the plug gaps were right, plug leads firmly on - and it still had the problem. Then it seemed to clear itself and it was soon ripping up the tarmac. OK I lied about the tarmac but it was going just fine so hopefully that's it. Whatever it was.

Mind you it was cold and I hadn't put all my kit on so I didn't go more than a few miles - but tomorrow I'll give it a longer run and see what happens.

Cheers
Mike

PS Thanks to Beezermac for his kind offer of help.

[Felters]

Cleaned out the main jet bowl - and it did need cleaning. Gave it a good 25 mile run round the local country roads and all is well. A lesson learnt.

Many thanks for all your help.

Mike