charliechitlins

There are specs. Leave a little slop.

unless you can have electrical components tested, you're stuck with elimination. Sparkplug and cap, HT lead, kill button and associated wiring, other wires (ground), flywheel key... If none of that does it, you need to buy a Sher....uh...I mean...you can start going after coil/stator/black box.

You should also say what part of the world you're in. Leeds or Louisiana?...it would make a difference.

You can ride awhile before you grease the stem and swingarm. Do the dogbones and wheel bearings too. For the wheel bearings, the seal has no shoulder and can be carefully pried out with a small screwdriver or pick. If you can find some 'external gear lube' like they slather on bevel/worm gears on construction equipment, that's good stuff. Tire pressures between 3 and 5 for rear (less for muddy/soft) and 5-7 for front. Next time you find some mud, experiment. 2psi difference in a tire in the mud can be huge. I'd also suggest finding pressures you like and pushing on the tire to feel what it's like. Maybe some low pressure gauges are OK, but not mine. I have to go by feel. Also...I can't see the bike too well, but I've seen a lot of offroad bikes where the starting point for handlebar adjustment is in line with the forks, but on a trials bike, you should start with about vertical. Maybe you need a few personal tips and lessons...we know how the riding is at your place, but how's the food and sleeping accomodations? Did anybody tell you that when you join the bulletin board, you have to host a riding weekend?

If the flywheel has only slipped a little, it could make the power soft on bottom, but be really noticeable on top.

Another vote for the flywheel key. The timing being way off can set stuff on fire.

I guess the answer would be to take the leg out, turn it upside-down, take the bolt out and check it out. I suppose there should be a sealing washer there. Maybe it was left out. Check for cracks. The possibility of a crack would make it a real bad idea to ride before you check it out.

I clean everything up real well with brake cleaner and a wire brush and run a bead of silicone in both channels where the band sits. I also silicone all around the valve. If I had a new band and a new rim, I'd skip the silicone. I use the spacer. I put the hole in the band over the hole in the rim, and everything is so slippery from the silicone that I just push on the valve stem and I can feel when the spacer pops through the hole in the band. I think the 2 challenges are to squeeze out air bubbles, and not to pull the band near the valve so the hole becomes oval and pulls out from under the valve. With a little practice, the whole thing takes 10 minutes.

That looks like motorcycle paradise! Any jobs out there?

I often find it hard to tell if a bike is running rich or lean when it's missing. The symptoms are similar. I usually get the bike to misbehave, then reach for the choke(enrichener) and open it just a little and see if the symptoms get better or worse. You mention it happening in sections, but you also said it happens after prolonged high-speed running. Is it both?

Could be running out of fuel from sustained speed. Try setting petcock on reserve. Check fuel line, filter (if you have one), gas tank vent and float level.

I think you're going to spend a lot more time with one leg on either side of the bike when you get a trials bike! That first pic is amazing. Do you carry a grappling hook and rope in case you get off line?

Love that red trellis frame! Can you say Ducati?

It doesn't seem to me that the 4-stroke has the same kind of disadvantage in trials as it does in MX. With 4-stroke technology being what it is, a 250 4T could have a big advantage over a 125 2T, and the quality of the sections could really highlight the advantage. This kind of stuff has been tested by time, though...ever since the British OHV 500s were allowed to compete in class C with the American 750cc sidevalves in the 1940s.

Bonoing!!! Is that a common term now, or a one-off custom Ringo-ism?

There seems to even be something that bears a passing resemblance to a seat.

I think the intake may have been lengthened a little, too. It would be nice if somebody had all the mods to this bike on record because it's a ripper.

That trick only works for bearings. If you did anything to a seal temperature-wise, I'd be sure it's warm enough to be pliable.

Also...if you have the 'standard' arrangement of 4 base nuts at the 4 corners of a square base, be careful about the integrity of that base. Consider making washers as large as you can to distrubute the pressure of the base nuts. And make sure to re-torque after break-in. Any loose-ness could snap an ear off. I deal with a lot of this with Indians. You may even want to consider welding a 2-piece collar on top of the whole base, thereby putting the 5mm you took off back on top.

There are also people who make pistons. It's a little expensive, but probably not as bad as you'd think.

Ever since the '70's I have been prying up the wipers and packing some vaseline under them. The wiper keeps most of the vaseline in, and it keeps dirt away from the seals.

Harley and Indian used this idea in the '40s and it worked well. They used a small venturi suspended with struts in the middle of the large venturi...it became known as a "bombsight) venturi and they were bolt-on horsepower. Although...comparing a GG to a '48 Harley might not be a good idea...

Basic rule is about .001" clearance for every inch of bore. Any possibility of milling the top of the barrel so the ports will stay where they belong? Honestly, I would try just living with the extra 5mm before you start going crazy. See how it runs before you go cutting hard-to-find parts. You could lap the head to the cylinder so you could run with no head gasket and close up the squish area a bit. I have a 4-stroke bike (Harley), where the piston misses the top of the barrel by a MILE, and it runs great. Kicks easy too!

Do I see dogbones and a cast lower yoke? Doesn't look like all Scorpa parts. Don't think swingarm is Scorpa either. Is it a custom?