Trials motors

[Lew Mayer]

I have mudlark which I think has a 6B motor. Is this possible or did all the trials bikes come with A motors? I realize someone could have switched them. I was going to check the front bolt size like past posts say. See,someone used the search engine. 8mm is A and 10mm is B,right?
 
Lew Mayer
Dennis Jones,HELP! I gotta get ready for Mid-Ohio.

[desmond197]

I have seen them with both motors. Mine has the 5A iron cylnder radial head with a five speed bottom. I have seen them with the iron cylnder Butch head as well as 6b with the radial head. They got different deals on these motors at different times.

[Kip Kern]

Lew  The last two Mudlarks I messed with had  6B's in them.  I removed my 6B and built a 5A with the heavy crank.  Besides, no use for a 6 speed in most dirt machines.[?]

[Lew Mayer]

Yeah,Kip,that's what I'm thinking about doing. I'll look for a cheap one to rebuild at Mid-Ohio.

Lew Mayer

[Kip Kern]

Remember, there are two types of 5 speed engines, the later with a two piece shifting arm, larger clutch 41.5mm, utilizing the same mainshaft/key as the 6 speed, with 16005 bearing.  And the earlier 5 speed that has the smaller clutch 39.5mm, one piece shift arm, 16004 mainshaft bearing and uses the smaller selector rod and key.  The latter, I think is better as the NOS smaller keys are available, tons of them, and the tranny is easier to adjust, .913 off the left case face when in third gear.  Both use the same tranny gears with the 3mm spacers.  Both shift bosses use the 4 tooth cog, I pitch the shift lock device.

[Lew Mayer]

Kip you mean the one piece shift arm is better? Also, can you get away without the shift lock mechanism? That would be great if it stays in gear. I might need to call you by phone to pick your brain if that's OK.

Lew Mayer

[Kip Kern]

Lew 765-668-8038 after 6pm.  I have never had any problem with either, for me, the one piece is easier to maintain and adjust.  The two piece offers more adjustment capabilities but is more confusing for most to adjust and maintain.  All in all, in either case, if the KS shaft is shimmed properly inside the engine, the transmission is built correctly (don't forget a new selector rod, detent cups/springs , shift key)and the shift boss is installed/shimmed properly all followed up by proper adjustment of the shift arm, the bike will shift properly.  I have a ton of the shift locks and cogs for Sachs if you need them, I just never use them.[xx(]