1978 BMW R100/7 - Airhead project
- Thread starter andrew6v
- Start date
andrew6v
Active Member
I noticed a bit of an issue today.
I was rotating the engine using the rotor bolt at the front of the bike while setting the timing, but the bolt is starting to strip, so I figured I'd pop it in 5 gear and spin the rear wheel to rotate it.
The issue is that the rear wheel doesn't want to spin in 4th/5th gear? I figure it should spin by hand relatively easily but it doesn't.. We started up the engine and put it in 4/5 and released the clutch a bit and the wheel spins in 4th/5th, seemingly without issue.
Any ideas what could be jamming it up that it's difficult to do by hand?
I was rotating the engine using the rotor bolt at the front of the bike while setting the timing, but the bolt is starting to strip, so I figured I'd pop it in 5 gear and spin the rear wheel to rotate it.
The issue is that the rear wheel doesn't want to spin in 4th/5th gear? I figure it should spin by hand relatively easily but it doesn't.. We started up the engine and put it in 4/5 and released the clutch a bit and the wheel spins in 4th/5th, seemingly without issue.
Any ideas what could be jamming it up that it's difficult to do by hand?
andrew6v
Active Member
Yeah I realized that was the issue. My dad is pretty stubborn having been an electrical technician for the navy for thirty years and the Clymers does say to pull the plugs, but he knew that wouldn't make a difference from an electric standpoint and felt it wasn't necessary :
. But in retrospect it's just to release compression haha
I've yet to get the timing set proper as I was out of province, but I"m hoping to get that and the carbs dialed in sometime this week.
Andrew
. But in retrospect it's just to release compression hahaI've yet to get the timing set proper as I was out of province, but I"m hoping to get that and the carbs dialed in sometime this week.
Andrew
andrew6v
Active Member
So I got the bike running, however I'm having an issue with pretty severe valve noise coming from one valve in one of the cylinders. You can basically hear it in this video when I get close to the right side cylinder here: https://www.instagram.com/p/BFfPAWyMxvx/?taken-by=andrewveinott
It's not the clearance, nor rocker endplay (as they can get loose on these bikes). It doesn't affect the running of the bike, as there is a ton of compression, and I've ridden it around the neighbourhood.
I'm going to take apart the rocker assembly and rebuild it as i'm pretty sure if it's not hitting square on the valve stem it can lead to a lot of noise. Besides that anyone have any ideas as to next steps? I guess it's possible I'll need a new valve & valve seat, as I guess it can get loud if it has worn down a fair bit. The bike's odometer doesn't work but is sitting around 90k km so it's had use.
I'm having a bit of an issue with the timing, I was using static timing, and the bike basically wanted to be fully advanced according to the static timing, so it has some hesitations at about a 1/4 throttle (mostly when just holding it there to keep the speed). It really goes though if you come onto it though.
We also went through the electrics, as there were some bad grounds (one ground wire was just dangling lol, no wonder the turning lights weren't working proper. It was street legal as I got a 10 day leeway period on getting it safety-inspected, but now that's over, and it likely won't pass because the front brake light switch is shot, which is on order.
Anyways this is how it sits today after a bit of clean-up, I would say it takes a picture better than it actually looks up close, but that's okay ;D It was kind of cool I took a spin down the street to meet my folks at a local bar for a minute, and I stepped back out and three people were checking out the bike haha an older couple bought one for their honeymoon in 1979, and toured the isle of mann, the other guy just thought it was really cool. These airheads aren't very common around here, and it was pretty neat to get that much attention on my very first drive.
It's not the clearance, nor rocker endplay (as they can get loose on these bikes). It doesn't affect the running of the bike, as there is a ton of compression, and I've ridden it around the neighbourhood.
I'm going to take apart the rocker assembly and rebuild it as i'm pretty sure if it's not hitting square on the valve stem it can lead to a lot of noise. Besides that anyone have any ideas as to next steps? I guess it's possible I'll need a new valve & valve seat, as I guess it can get loud if it has worn down a fair bit. The bike's odometer doesn't work but is sitting around 90k km so it's had use.
I'm having a bit of an issue with the timing, I was using static timing, and the bike basically wanted to be fully advanced according to the static timing, so it has some hesitations at about a 1/4 throttle (mostly when just holding it there to keep the speed). It really goes though if you come onto it though.
We also went through the electrics, as there were some bad grounds (one ground wire was just dangling lol, no wonder the turning lights weren't working proper. It was street legal as I got a 10 day leeway period on getting it safety-inspected, but now that's over, and it likely won't pass because the front brake light switch is shot, which is on order.
Anyways this is how it sits today after a bit of clean-up, I would say it takes a picture better than it actually looks up close, but that's okay ;D It was kind of cool I took a spin down the street to meet my folks at a local bar for a minute, and I stepped back out and three people were checking out the bike haha an older couple bought one for their honeymoon in 1979, and toured the isle of mann, the other guy just thought it was really cool. These airheads aren't very common around here, and it was pretty neat to get that much attention on my very first drive.
TJGM
Of Wild Kind...
Maritime said:
Loraine !
Sorry, just going through this now. Charlie ( the son ) and Adrian have been amazing for me. They get anything I need for my r100, and will explain / tell you how anything works. Plus they have tons of old shit laying around. I lost a valve stud and nut and they one in a junk drawer. Amazing people to deal with.
Andrew, once this thing is road worthy we should meet in the middle somewhere and go for a rip !
~T
andrew6v
Active Member
So took apart the rocker and noticed the exhaust valve is fairly loose, which is likely the culprit. Put it back together and made sure it's very square as that leads to some valve noise, and it made a difference, but is still loud. I would say the valve and valve seat are quite worn at this point, which makes sense as it was definitely worn compared to the intake side and took a lot more grinding to ensure it didn't leak. So that likely means some new expensive parts and a trip to a machine shop. Shouldn't be terribly costly hopefully.
Good to hear TJGM, I'll give Adrien's a call and see how she goes, I've typically been using Motobins, as their prices plus shipping from the UK have been less than any Canadian BMW parts supplier I've found, particularly with the downward swing in the pound compared to CAD. I'd be down for meeting half-way and going for a rip haha
Good to hear TJGM, I'll give Adrien's a call and see how she goes, I've typically been using Motobins, as their prices plus shipping from the UK have been less than any Canadian BMW parts supplier I've found, particularly with the downward swing in the pound compared to CAD. I'd be down for meeting half-way and going for a rip haha
andrew6v
Active Member
So there was a hesitation at around quarter throttle (basically where you'd hold it to keep current speed which was annoying), even with the carbs vacuum synced, and looking at all the throttle cables to make sure they aren't kinking or something, it was still there.
I figured it was the timing as we were having an issue setting it, as regardless of where I'd set the advance/retard the appropriate timing marks wouldn't show up on the fly wheel. Considering getting at the points and adjusting them were a hassle (and I bought brand new points, and the connections were poorly soldered such that it would actually make the bike not start ) I decided to just replace it with an electronic ignition.
I'm really happy I did, we were able to set up the timing perfectly to spec, and I took it for a spin and it no longer has any hesitations, and revs up perfectly ;D ;D
I realized I think it was the advance mechanism which was frigged up. It has two springs, and one was noticeably looser than the other. Funny how so many little things can affect the running of the bike.
Anyways yesterday was a good day
I got the exhaust valves and seats in the mail, so just need to get a shop to put those in, and hopefully that will fix the valve noise issue.
I figured it was the timing as we were having an issue setting it, as regardless of where I'd set the advance/retard the appropriate timing marks wouldn't show up on the fly wheel. Considering getting at the points and adjusting them were a hassle (and I bought brand new points, and the connections were poorly soldered such that it would actually make the bike not start
) I decided to just replace it with an electronic ignition.I'm really happy I did, we were able to set up the timing perfectly to spec, and I took it for a spin and it no longer has any hesitations, and revs up perfectly ;D ;D
I realized I think it was the advance mechanism which was frigged up. It has two springs, and one was noticeably looser than the other. Funny how so many little things can affect the running of the bike.
Anyways yesterday was a good day
I got the exhaust valves and seats in the mail, so just need to get a shop to put those in, and hopefully that will fix the valve noise issue.
JustinLonghorn
No Purple Hearts, No Blue Ribbons
Very nice, man.
JustinLonghorn
No Purple Hearts, No Blue Ribbons
Next do the Enduralast charging system!
andrew6v
Active Member
JustinLonghorn said:
I heard it makes a big difference to the bike, but so far what I got is working quite well it seems. The bike has extra gauges (oil pressure and voltmeter) and it shows me a good 13ish volts being charged when booting around the neigbourhood.
Do you find it makes a significant difference?
