Saturday, 8 January 2011

Race Bike Winter Rebuild

Well...... 2010 is over so lets move swiftly on to 2011!

Plans for this winter are a full strip and rebuild of the scooter and a new paint job for 2011.  Dave Cramptons Group 6 is also paying a visit to the workshop for a new paint job too - so it's going to be a busy winter as i also have the special Jet200 on the go too! More on that one later!

So......  between Christmas and new year I took the scooter down to Chalky's workshop at Replay Scooters - well its any excuse to play scooters at Christmas eh?

The engine had run pretty badly at the last round at Three Sisters with an air leak making the engine revs rise and  basically scream with the throttle closed - which round Three Sisters ain't fun I can assure you!  So we'll pass over that one!

So first job was to try and track down the leak.....  stripping off the barrel head and piston revealed nothing too obvious, but once the flywheel was off the problem revealed itself.

The exhaust mount on the left hand side is straight off the engine bolt and could do with a bit more rubber mounting really, which will be changed for 2011.  The extra vibration induced had loosened a mag housing nut allowing it to come slightly loose, and around that bolt the gasket had been blown out, so the air leak was indeed pretty big!

Further inspection showed that the mag bearing was also well worn so needed replacement, alongwith the piston and rings which were ready only for the bin lol.

So a pleasant afternoon was spent stripping, cleaning and replacing everything.  Luckily Ciro was on hand with a new Suzuki Piston which was a result as they are now getting increasingly hard to find.  Amazingly the barrel wear is still minimal - testament to the Rock Oil supplied by sponsors Lambretta Cottage.

Once everything was back together and checked over we had some time to do some base runs on the Dyno.
Its important to do this to get a base graph to work from for some winter developments that are planned.

First off is a new Carburettor.  The Mikuni TMX35 has been trouble free but the Dell Orto VHSB has more flexibility in fine tuning and is likely to produce a little more power.  Chalky is modifying the carb to give some improved results ( ssshhhhhhh   secret! ) and a new inlet manifold is likely.

The exhaust system is likely to be changed too.  The plan is to try a few exhausts and test on the dyno over the next month in order to experiment with what works best with the motor.  This whole exhaust malarky can be quite a black art and is not always the most logical science!

With a base run over it was back to base - leaving Chalky to play with some more exhausts.

A couple of days later a Guy Topper designed pipe was fitted and tried on the dyno.  It showed a good result with + 1.5HP, but most importantly it allowed the engine to rev on higher and was actually a whole 10mph faster on a 3rd gear run.

So..... a couple more exhausts to try over the next few weeks