Scooterotica

Right, I've been building an indian stage four top end and it just doesn't want to run properly. When you rev it the revs don't go down quickly, and once it has some heat in it the revs just stay continuously high... To me this sounds like an air leak?

The other day I removed the cylinder head and this show signs of leakage, so I glass faced the head and have since built the whole thing with a liberal smear of silicon. The barrel is a little tight at the base, but once torqued it sits flat with no gaps.

The timing is set quite conservatively ATM at 17', I checked this to make sure it wasn't too far advanced.

The jetting on a 30mm carb with a NK rally is;

128 Main
53 Pilot
AV264
X13 3rd clip down
40 Slide

I am really struggling to diagnose this and need to sort it ASAP, could have disturbed the flywheel side seals when I had the mag housing off? Could it be leaking from the mag housing gasket, I renewed with a fresh one?

Any suggestions much appreciated!

Jordan

hi fella, a leak tester kit is what you need, sure sticky did a test in an old scootering.
Usual checks at manifold , carb rubber ,exhaust and yes I would look at the mag housing gasket , and the seals for any oil seepage .
Not much help really but gives you a start

What he said ^
I would be looking at the carb first with those symptoms. Split rubber? Also looked at your jetting. How does it run? Reason for asking is that I went through the carb settings on the LCGB site the other day and came away with x7 needle 2 clips down, av 266, 50 or 55 pilot/needle jet and 125 main, 40 slide.. I am using a filter though. The only change I had to make on my set up was the atomiser as I had an av244 in. Mine now runs sweet.
IMO it is very rare to get an air leak behind the mag flange (watch twenty people post otherwise )
Finally you're getting pretty good at doing your engine work but double check the head. Sometimes (often) you're hear a squealing noise when kicking over if the gasket has gone.
Good luck Jordan

The rubber hasn't split, as that was first port of call

I think I will check the inlet manifold gasket tomorrow, as that's the last gasket face on the barrel I haven't checked. But, it looks really well sealed, but worth checking now.

If no joy, I will look at the mag flange and flywheel side seals.

I haven't rode the scooter so can't really comment on the jetting just yet, but do you mean 264 and not 244?

Cheers

There's a thread on the Other site about a home made leak test using a bicycle tube, might help track it down.. Definitely sounds like an air leak.

I have just copied the leak tester mentioned above using a bike inner tube, and it does work. the leak on the engine i was looking at required a compressor to pump up the inner tube due to leak being quite big and foot pump wouldn't provide enough air.
The symptoms you describe are exactly the same as the engine i went to look at, get the leak sorted then look at carb settings once you can ride it.

Be interested to know how it goes with the NK Rally on as I am about to build a St4 200 and that is one of the exhausts on the guys list.

rosscla wrote:There's a thread on the Other site about a home made leak test using a bicycle tube, might help track it down.. Definitely sounds like an air leak.

One here ...... http://scooterotica.org/forum/viewtopic ... 12&t=26427

Inlet manifold gasket changed and no joy, struggling to figure this out... No obvious leakage from the mag housing or the seals, all looks tight.

Is it just thst it's simply too learn? It's also used with a 60mm crank, 110 rod and mtech?

For the sake of a bike inner tube and a couple of jubilee clips, I'd do a leak test first to check everything is OK.your comment that the cylinder is a bit tight in the spigot gives cause for concern. I'd look for any cracks around any cylinder studs, mag housing seating correctly. Have you tried spraying around gasket faces to check for leaks?o