139FMB gear issues

DrKassler · 09-13-2024, 05:40 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, 10:25 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 · 09-15-2024, 07:23 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.

Crossbar · 09-15-2024, 10:41 AM

Sorry, not familiar with that motor but if it's a mesh flat screen it is probably under the clutch cover. I would make sure the clutch cable is correctly adjusted so it's properly disengaging the clutch. I'd be tempted to try a 15w40 oil. Many on this site run the common Shell Rotella 15W40 and works well with the wet clutches. I run that in all mine but I don't have any 50cc engines.

DrKassler · 09-15-2024, 11:33 AM

Checked the clutch cable and adjusted the clutch, no improvement. Wonder if the clutch sticks a bit from the friction parts being perhaps damaged from using the wrong oil. Will change complete clutch to rule it out, just about 30 euros and easy job so willing to take a gamble. Will look into different oil viscosity if needed.
Hopefully it will work without changing the gear selector barrel or something a like.

krat · 09-15-2024, 07:22 PM

If this is a manual transmission with the gears sharing the engine space 20/50 car oil is not what you need to be running. Auto oil does not contain the additives a motorcycle transmission/wet clutch needs.

You need oil blended for motorcycle use with anti-slip agents incorporated. 99% sure that is what is causing your problem.

You can get it at most auto supply outlets. It will be labeled for motorcycle use.

DrKassler · 09-16-2024, 04:28 AM

Hi! To clarify, it has previously been run with the wrong kind of oil. Most of all it has been standing still for about 6 months with the wrong oil.
From 300km to 1500km where we are now it has had 20w/50 motorcycle oil (MOTUL 3000 4T 20W50).
Change of oil (again) and new clutch is the next step. About 10 days before the parts arrive.
Will get back.

DrKassler · 09-29-2024, 10:16 AM

Clutch changed.
Before:
https://photos.app.goo.gl/g5qEgGxkDmAZhbBp8

The thread of the crankshaft end were in bad condition although its hasn't been repaired. Managed to clean the thread a bit and the new nut was ok to tighten but the thread needs to be redone next time someone is there. I read M14x1 somewhere, anyone that can confirm?
https://photos.app.goo.gl/oPCdA5S87NGgbn2G9

Test riding is done as I write but I have low expectations. But feels good to know the clutch is ok and hasn't been facing the wrong type of oil.

Can anyone explain how the actual clutch actuation works, I understand the mechanics of the clutch itself but I couldn't see any connecting rod so to speak between the clutch arm and the insert in the bearing in the clutch pressure plate itself.

The inside of the engine cover is shown here with just a very small hole where the clutch actuator arm is located:
https://photos.app.goo.gl/D8N86x2DczCnVG1N9

Will tell more after the test ride.

DrKassler · 09-30-2024, 05:02 AM

Seems it doesn't jump out of gear anymore. Still, going in to neutral from standstill and in 1st gear is almost impossible with the engine running. I guess it's just how it is.
We'll go back to sleep until the next issue arises. :-)

tomaitistomas029 · 10-09-2024, 07:31 AM

It sounds like you're dealing with some common gearbox issues on your Romet Division 50cc. Here are a few things to consider for each of your problems:
For getting into neutral, the difficulty could be due to misalignment or wear in the shift mechanism or linkage. Ensure that the gear lever is properly adjusted and not bent. You might also want to check the shift pawl for wear or damage.
Regarding the issue of getting into first gear, especially when the engine is running, this could indicate a problem with the clutch not fully disengaging or internal gearbox issues. Since you've mentioned the clutch is adjusted correctly, consider checking the clutch cable for fraying or binding.

09-13-2024, 05:40 AM	#1
DrKassler Join Date: Sep 2024 Posts: 6	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

09-15-2024, 07:22 PM	#6
krat Join Date: Nov 2019 Location: KY Posts: 277	If this is a manual transmission with the gears sharing the engine space 20/50 car oil is not what you need to be running. Auto oil does not contain the additives a motorcycle transmission/wet clutch needs. You need oil blended for motorcycle use with anti-slip agents incorporated. 99% sure that is what is causing your problem. You can get it at most auto supply outlets. It will be labeled for motorcycle use. __________________ %90 of the Chinese motorbikes ever made are still on the road. The other %10 made it back home.
	0

09-13-2024, 10:25 PM	#2
Crossbar Join Date: Jun 2024 Posts: 83	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

09-15-2024, 07:23 AM	#3
DrKassler Join Date: Sep 2024 Posts: 6	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

09-15-2024, 10:41 AM	#4
Crossbar Join Date: Jun 2024 Posts: 83	Sorry, not familiar with that motor but if it's a mesh flat screen it is probably under the clutch cover. I would make sure the clutch cable is correctly adjusted so it's properly disengaging the clutch. I'd be tempted to try a 15w40 oil. Many on this site run the common Shell Rotella 15W40 and works well with the wet clutches. I run that in all mine but I don't have any 50cc engines.
	0

09-15-2024, 11:33 AM	#5
DrKassler Join Date: Sep 2024 Posts: 6	Checked the clutch cable and adjusted the clutch, no improvement. Wonder if the clutch sticks a bit from the friction parts being perhaps damaged from using the wrong oil. Will change complete clutch to rule it out, just about 30 euros and easy job so willing to take a gamble. Will look into different oil viscosity if needed. Hopefully it will work without changing the gear selector barrel or something a like.
	1

09-16-2024, 04:28 AM	#7
DrKassler Join Date: Sep 2024 Posts: 6	Hi! To clarify, it has previously been run with the wrong kind of oil. Most of all it has been standing still for about 6 months with the wrong oil. From 300km to 1500km where we are now it has had 20w/50 motorcycle oil (MOTUL 3000 4T 20W50). Change of oil (again) and new clutch is the next step. About 10 days before the parts arrive. Will get back.
	0

09-29-2024, 10:16 AM	#8
DrKassler Join Date: Sep 2024 Posts: 6	Clutch changed. Before: https://photos.app.goo.gl/g5qEgGxkDmAZhbBp8 The thread of the crankshaft end were in bad condition although its hasn't been repaired. Managed to clean the thread a bit and the new nut was ok to tighten but the thread needs to be redone next time someone is there. I read M14x1 somewhere, anyone that can confirm? https://photos.app.goo.gl/oPCdA5S87NGgbn2G9 Test riding is done as I write but I have low expectations. But feels good to know the clutch is ok and hasn't been facing the wrong type of oil. Can anyone explain how the actual clutch actuation works, I understand the mechanics of the clutch itself but I couldn't see any connecting rod so to speak between the clutch arm and the insert in the bearing in the clutch pressure plate itself. The inside of the engine cover is shown here with just a very small hole where the clutch actuator arm is located: https://photos.app.goo.gl/D8N86x2DczCnVG1N9 Will tell more after the test ride.
	0

09-30-2024, 05:02 AM	#9
DrKassler Join Date: Sep 2024 Posts: 6	Seems it doesn't jump out of gear anymore. Still, going in to neutral from standstill and in 1st gear is almost impossible with the engine running. I guess it's just how it is. We'll go back to sleep until the next issue arises. :-)
	0

10-09-2024, 07:31 AM	#10
tomaitistomas029 Join Date: Oct 2024 Posts: 2	It sounds like you're dealing with some common gearbox issues on your Romet Division 50cc. Here are a few things to consider for each of your problems: For getting into neutral, the difficulty could be due to misalignment or wear in the shift mechanism or linkage. Ensure that the gear lever is properly adjusted and not bent. You might also want to check the shift pawl for wear or damage. Regarding the issue of getting into first gear, especially when the engine is running, this could indicate a problem with the clutch not fully disengaging or internal gearbox issues. Since you've mentioned the clutch is adjusted correctly, consider checking the clutch cable for fraying or binding.
	0