139FMB gear issues

DrKassler · 09-13-2024, 04:40 AM

Hi!
We've got a Romet Division 50cc with a 139FMB 4-speed manual.
It has only done about 1500 km's but are showing issues with the gears.

Issue 1:
It's really tricky to get it into neutral.
From 2'nd to neutral you can barely put your foot on the gear selector. If just a bit more force is used it will go into 1st.
From 1st you most of the time end up in 2nd instead of neutral.
--
Issue 2:
At standstill and in neutral it's tricky to get into 1st and sometimes it's impossible until you switch the engine off.
--
Issue 3:
It goes from 1'st or 2'nd into neutral while riding by itself. Not very common but it happens once or twice at each ride.
--

The clutch is adjusted and releases properly and has no slip while driving.
Can anyone give me some advice on what to do?

How hard is it to split the engine and replace the gearbox barrel if it is faulty for example? Is there good videos available for example?
I'm a quite experienced mechanic but new to bike engines.

Thanks in advance!

Crossbar · 09-13-2024, 09:25 PM

When I read your issue one and two I'd say sometimes you just have to get used to the transmission. Most of the time if it's a 1 down, x up, I always go to first then neutral. On some of my bikes I have to let the clutch out just a little, pull it back in and then try for neutral. If it goes to 2nd instead I go back to 1st and try again. There's a ground off lope in between the 1st and 2nd gear lope that lets the roller rest/lock in the neutral position. It's just a matter of learning what your particular trans likes.

Your issue 3 however throws that out the window. It shouldn't be popping out of gear like that unless for some reason it wasn't fully in gear or maybe your foot slightly hit the shifter by mistake. There's some youtube videos on how a mc trans works to give you a visual on what's going on when shifting.

It almost sounds as if your clutch could be slightly dragging (not fully disengaging). That would make it hard to shift into gears from neutral.

DrKassler · Today, 06:23 AM

Thanks for your answers!
I think you might be right, when I tested the bike yesterday I agree that there might be something going on with the clutch. It´s our sons bike.
When we 1st got the bike it had only done 250km´s but had been standing still for a long time. The previous owner had changed the oil to 20/50w for vintage cars. The clutch worked poorly and at one point it stopped releasing at all even though we adjusted it as in the ws manual. After contact with the original distributor we got the info to change to 20w50 oil specificly for bikes and after that the clutch worked again.
The bike has though always been a bit strange with the gears so maybe the clutch is still off in a way.
We are supposed to change the oil now again according to the service interval so that´s the plan and then adjust the clutch again.
According to the service interval we are also supposed to clean the oil filter. It is done by removing the whole RHS engine crankcase cover right? Any knowledge about this?

https://photos.app.goo.gl/sxbfGXeN3dLBUieDA

Appreciating all and any help.

09-13-2024, 04:40 AM	#1
DrKassler Join Date: Sep 2024 Posts: 2	139FMB gear issues Hi! We've got a Romet Division 50cc with a 139FMB 4-speed manual. It has only done about 1500 km's but are showing issues with the gears. Issue 1: It's really tricky to get it into neutral. From 2'nd to neutral you can barely put your foot on the gear selector. If just a bit more force is used it will go into 1st. From 1st you most of the time end up in 2nd instead of neutral. -- Issue 2: At standstill and in neutral it's tricky to get into 1st and sometimes it's impossible until you switch the engine off. -- Issue 3: It goes from 1'st or 2'nd into neutral while riding by itself. Not very common but it happens once or twice at each ride. -- The clutch is adjusted and releases properly and has no slip while driving. Can anyone give me some advice on what to do? How hard is it to split the engine and replace the gearbox barrel if it is faulty for example? Is there good videos available for example? I'm a quite experienced mechanic but new to bike engines. Thanks in advance!
	0

09-13-2024, 09:25 PM	#2
Crossbar Join Date: Jun 2024 Posts: 64	When I read your issue one and two I'd say sometimes you just have to get used to the transmission. Most of the time if it's a 1 down, x up, I always go to first then neutral. On some of my bikes I have to let the clutch out just a little, pull it back in and then try for neutral. If it goes to 2nd instead I go back to 1st and try again. There's a ground off lope in between the 1st and 2nd gear lope that lets the roller rest/lock in the neutral position. It's just a matter of learning what your particular trans likes. Your issue 3 however throws that out the window. It shouldn't be popping out of gear like that unless for some reason it wasn't fully in gear or maybe your foot slightly hit the shifter by mistake. There's some youtube videos on how a mc trans works to give you a visual on what's going on when shifting. It almost sounds as if your clutch could be slightly dragging (not fully disengaging). That would make it hard to shift into gears from neutral.
	0

Today, 06:23 AM	#3
DrKassler Join Date: Sep 2024 Posts: 2	Thanks for your answers! I think you might be right, when I tested the bike yesterday I agree that there might be something going on with the clutch. It´s our sons bike. When we 1st got the bike it had only done 250km´s but had been standing still for a long time. The previous owner had changed the oil to 20/50w for vintage cars. The clutch worked poorly and at one point it stopped releasing at all even though we adjusted it as in the ws manual. After contact with the original distributor we got the info to change to 20w50 oil specificly for bikes and after that the clutch worked again. The bike has though always been a bit strange with the gears so maybe the clutch is still off in a way. We are supposed to change the oil now again according to the service interval so that´s the plan and then adjust the clutch again. According to the service interval we are also supposed to clean the oil filter. It is done by removing the whole RHS engine crankcase cover right? Any knowledge about this? https://photos.app.goo.gl/sxbfGXeN3dLBUieDA Appreciating all and any help.
	0