Ariel Owners Motorcycle Club

Fettling is coming along nicely. My lovely FH idles well and rolls gently up as I open the throttle. It tends to spit a bit and stop itself, but starts again first kick - now I’ve figured out what’s on/off/ what’s 1/4 throttle etc. if I run it faster and then drop back to idle, unless I’m careful, it stalls. So if I just shut the throttle - stops.

The problem is possibly emerging as you can see in the piccie. The exhausts are going gold at the top and blueing slightly further down. They are also *blimmin* hot, as is the head by the exhaust ports etc.

I suspect the timing needs strobing - so far static-set manually (a pencil measured at 11/32 BTDC down the plug hole (on the up stroke)), fully advanced A/R unit, and marks lined up nicely, but wonder if my BTDC measurement was too crude?

I still think it’s a bit retarded so I’ve got burning fuel-air going out of the exhaust port too early? Advance it slightly first and then strobe it? Do a better job of measuring BTDC? Use a timing disc (how many degrees please?). It’s so easy to start and runs nicely (grey plugs) I’m wondering what to meddle with!

Firstly though - do those pipes give an indication of what’s up?

Any advice from sage, wizened ignition elves greatly appreciated.

Hi Martin

I had similar issues timing my FH, the access to the points is pretty obscured by the PCC making the fag paper route problematic. I bit the bullet and bought one of these:

http://www.aoservices.co.uk/info/MTL.pdf

It makes timing a doddle and, in my opinion, is money well spent, (when you consider the cost of exhausts etc).

The discolouration of my exhausts was due to retarded timing and the tool enabled me to sort it, finding a point BTDC is quite easy and accurate, the errors are far more difficult to eliminate when setting the points

Regards Mick

Thanks Mick - possibly forgot a useful bit of information: I bit a bigger bullet and went electronic, so I (supposedly simply…) set the BTDC, and line up the trigger rotor with the sensor that ‘pings’ the box of brains and tells it to blast a coil or two. The sensor can be manually rotated earlier or later around that sensor to advance/retard the trigger moment. Mark 1 eyeball however (even with varifocals) may be the weak link here. Hence the possible need to strobe the whole thing…. From the colour though, would you concur that it’s triggering too late?

Your problem may well be mixture rather than ignition timing.
My experience with the twins - a long time ago now - was that they
weren't that sensitive to ignition timing as long as they had the standard
compression pistons.

And yes, thin, poor-quality chrome blues much quicker than good
quality - not that I'm implying yours are anything but good.

Hi Martin

My edit crossed with your reply.

Yes, I think your timing is a little retarded, I'd just try advancing it incrementally and see how the bike drives. Do you have an IR thermometer that you can use to observe the head temperature at the exhaust? Mine runs at about 240 degrees C now.

Regards Mick

With spitting back and blueing pipes, I would diagnose weak mixture.

If the jets are right, the only way it will be lean is if it's leaking air on the inlet tract (carby mount or inlet valve guides).

Are the pipes Stainless? If so, the yellowing effect is quite common with heat. Obviously the blue is a different matter.