In a previous post some time in May I wrote about how my 350 Jawa had expired in the driveway outside my garage. I got the engine out and sent it off to Andy at Moll Springs Motorcycles ( http://www.mollsprings.co.uk/ ) to be stripped down and assessed. As I thought, the left hand big end bearing had failed but the true extent of the damage I would not have guessed. The bits of bearing rattled about in the bottom of the engine then came up through the transfer ports. Evidence of this was all over the top of the piston and the inside of the cylinder head, but what I hadn't realised is that one of those bits managed to smash the bottom of the skirt off the piston, making more bits to rattle about!
When the gearbox was stripped it was seen that a dog had broken off one of the gears too (there should be four, the missing one is at 9 o'clock). It was laying in the bottom of the gearbox portion of the crankcase casting. I had no inkling of this as it changed gear perfectly.Luckily I have two engines and the other one has donated a good gear box and pistons, barrels and heads which are like new. I have ordered a set of big end and con rod kits from a Jawa dealer down south and I am awaiting the arrival of them from the Czech Republic. I should be back on the road with this bike in the Spring.
ey up mark, what a bummer!, you certainly have endless hours of fun ahead sorting this one out! as a matter of interest which gear caused the failure?, i have trouble with my third gear on my mz racer and i have also changed my fifth gear for a closer ratio, i found some work fettling the selector forks has made the gearchange a lot more positive, cadwell park coming up next weekend, can't wait!, regards, tim.
ReplyDeleteHi Tim. Good luck with the race. MZ 5 speed gearboxes can give third gear trouble, especially if the gear changes are rushed as obviously they will be under race conditions. I am not sure what the cure is, I bet Burwins know of one.
ReplyDeleteAll my MZs are 4 speed being all older models. The 4 speed box is very rugged but the gear change is awful and takes a lot of getting used to. The gearbox which has broken is off my Jawa, a nice bike to ride gently, but hardly of MZ quality in terms of design or construction, sadly.
Ride safe and enjoy!