My mate has the above bike. Today initially it wouldn't select 1st then he got it into 1st and couldn't select any other gears. Can the gearbox be pulled without splitting the crankcases? Is it a cassette type gearbox? Advise please

With regards to the clutch,what should he be looking for?

 

After your clutch cover is off take a look at the gear shift shaft, A common Beta issue is the weld that holds the selector on the end loften breaks free. Usually after an impact with an object or being used as a footpeg. Can be slid out clutch side and rewelded.. Best of luck

As stated above, it probably is not a transmission problem. It is a shifting problem which is located behind the clutch. Shift shaft to shift drum.

Check the rivet in the gear selector assembly, item 7 in the attached figure. If the rivet in the selector (item 8) comes out, or becomes loose, the transmission will not shift.

Thanks for the responses,all very helpful, any further information gladly received

Have you tried rocking the bike back and forth while pulling and pushing the gear lever? This sometimes works. Was there any issue with gear selection before this? Any unusual noises from the gearbox with engine running?

Things to make sure you do when you have the clutch cover off.   1)  Make sure you keep track of the shims on both the shift shaft and the kick start shaft.  2) Make sure item 15 is attached tightly to the shift drum , I have seen one of these not tight before.  Good luck.

Basically he bought the bike about a year ago, it got a new frame eventually under warranty, and we have slowly swapped it all over, this event was its first real outing ( nothing in the engine was tampered with, it was just transferred) the bike was running perfect and then he commented he couldn't select first, i had a go on it and it had all the other gears, then rocking it back and forth we got first, he was riding it and i think it jumped out of 1st, he clicked it into first and that was it, no more gears available and couldn't get it out of first. I asked him if he could change gear while riding it on the flat without using the clutch, he hadn't tried to.thats really all I know 

Edited March 26, 20188 yr by retromlc

Ok hes had the clutch apart and all.seem.to be in order, anything else before we have to split the engine?

 You have to remove the whole clutch assembly to get to the shifter and drum. How are you ever going to split a motor if you do not understand the basics of how this works. It has been this way on 2 strokes for 50 years. Did you even look at the service manual.

Thank for the critics, firstly i am not there i am posting on his behalf, so only repeating what he is saying, i am not asking you to do it but for some advice based on your experience, he has had the bike for a year but until the frame was swapped over wasn't ridden, which we did perfectly so we obviously have abilities.but not knowledge of the idiosyncratics of these particular bikes. Hence the questions.

Having spoken to him he's had it all apart and selector fork is not damaged and has intermittent selection, but had locked up again,the selector drum looks fine so engine out for a good look inside.

there was evidence of water contamination in gearbox oil with damage to clutch steel's, 

 Uh oh. Sat with water for a year. Now that is another can of worms.

Update, got a message saying it a broken tooth on the main shaft sprocket, parts arrived next day from lampkin, all together£135, pretty reasonable. Couple of hours and all back together, ran perfect at this weekend trial

Edited April 9, 20188 yr by retromlc