1971 cl100

benroloff

Active Member
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Finally got the pcb’s that I ordered for my little electronic ignition experiment a few days ago. I ended up with a short circuit on the first board and ruined it and a transistor, thankfully I ordered extras and I was able to get one together today and test it. I used a magnet spun by my drill and everything seemed to function well. None of the components got hot at all and it made spark and seemed to keep up just fine. My drill spins at 1500 rpm, which would be 3000 rpm at the crank, so I really wasn’t able to test up to high rpm but so far so good. I need to figure out how to mount a magnet in a trigger wheel though now. I am also really concerned about heat. Neodymium magnets loose their magnetic properties above about 200f if I am not mistaken, and it seems that it might get that hot under the points cover so if that happens I’m not sure what I’ll do


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benroloff

Active Member
cool. what does Dyna use in theirs for magnet type?

Im not sure, I looked briefly but didn’t find any info. It’s entirely possible that the magnet just doesn’t get that hot and so it doesn’t really matter, but in the event that it does become an issue I did find some neodymium’s that operate up to like 300f so I can always go to that. I can’t imagine the magnet getting any hotter than that


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irk miller

You've been mostly-dead all day.
DTT BOTM WINNER
Electronic ignitions use ceramic or hard ferrite magnets, which have a Curie point of 570 degrees fahrenheit.
 

benroloff

Active Member
Well when I bought this pig I never did a compression test, I just decided that it ran well enough for me, and if compression was a little low, so be it. A few days ago however, it was smoking out of the breather a little bit after some harder riding, so I pulled the oil cap off while it was running to see if there was some blow by. Well... there was a lot. So rather than continue to ignore the issue, I tore the bike down, and threw the engine up on the bench.
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It all came apart well, aside from being caked with an incredible amount of oil and dirt. So I got the head off, nothing looked to worn,cam looked ok, took the piston out, a little wear on the piston, but too soon to say if it’s bad without having it to the machine shop for measurements yet. I was just about to take the rings off to measure ring gaps, and then...
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I’ve heard of broken rings, but wow. This all just fell into my hands when I picked the piston up, how it didn’t just fall into the case when the cylinder came off, I don’t know. So I would imagine that some compression was slipping past the top ring lol. The cylinder looks ok though I think. No scoring, some wear, but nothing that Really jumped out at me, especially on a 50 year old bike, with 12,000 miles that were probably all ridden at full throttle. I can’t feel a lip or anything at the top of the cylinder, and none of the wear seems too crazy, but if anyone sees something I’m missing, please point it out.
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I’m going to try to get the piston and cylinder to the machinist tomorrow maybe to get some measurements, and I’ll go from there. The crank didn’t have any play in it either so i think I’m ok there. My really big concern right now is that a piece of the ring fell into the crankcase when I took the cylinder off or when I took the piston off, and I didn’t notice. I really don’t want to split cases, so my question is, can I just flush the oil a few times before I even try to start it up, and then a few times again after I start it I’d be ok? I don’t think anything fell down there, but I’d obviously hate to rebuild it just to have it suck up a piece of ring, but like I said, I’d really rather not split cases.


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pidjones

Over 1,000 Posts
Maybe some intent probing with a magnetic pickup tool? Also, compressed air (after getting the oil out) can move a lot of things. I've seen mechanics at their whits end because they had dropped a spark plug terminal nut down a plug hole. Old, experienced mechanic reached over with his compressed air nozzle and out it flew!
 

benroloff

Active Member
Maybe some intent probing with a magnetic pickup tool? Also, compressed air (after getting the oil out) can move a lot of things. I've seen mechanics at their whits end because they had dropped a spark plug terminal nut down a plug hole. Old, experienced mechanic reached over with his compressed air nozzle and out it flew!

I’m definitely planning on using a magnetic pickup tool, but I hadn’t considered compressed air. The guys that have been doing this stuff for years never cease to amaze me, and just when you think you have a pretty good idea of what your doing lol. Like I said, I’m pretty sure nothing fell in there but I’m going to take every precaution


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benroloff

Active Member
Dropped the cylinder at the machine shop today. Bore came back at 50.5, which is what it is from the factory, so a hone and some new rings and we should be back in business


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ex119x

Been Around the Block
Dropped the cylinder at the machine shop today. Bore came back at 50.5, which is what it is from the factory, so a hone and some new rings and we should be back in business


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Make sure you check the ring lands in your old piston. I would be concerned that they may be too wide given the damage of your old ring. Just look for excessive wear or damage. I might just spend the money for a new piston. A single piston isn't that expensive.
 

benroloff

Active Member
Make sure you check the ring lands in your old piston. I would be concerned that they may be too wide given the damage of your old ring. Just look for excessive wear or damage. I might just spend the money for a new piston. A single piston isn't that expensive.

Machinist said the same thing. There is some wear but it doesn’t seem too bad. He said it likely won’t be a perfect seal but it’s not gonna hurt anything. I’m not going to stress over it too much unless it ends up really affecting compression a lot. If that’s the case I’ll find a piston and put it in, it’s not a tough engine to tear down, but standard size pistons are getting though to find.


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benroloff

Active Member
Cylinder is back from machine shop, looks very nice, now just waiting on rings and some other engine stuff. I checked the oil filter today for the first time since I’ve owned the bike, which is stupid, I know I should’ve done it before now, but long story short there was a fair amount of metal shavings in it. Now, I’m not really sure where they could be from. The cylinder is not worn out or scored, so it’s not that, the crank seems to be in good shape, no up and down play so I have ruled that out. I guess it could be from the gearbox, but I doubt it. The only thing that really jumped out at me was that it looks like at some point in time the cam chain was adjusted way too loose and it was rubbing on the cylinder and head where it passes through, and that would certainly create metal shavings, and given how everything else on this bike was maintained by the previous owner I’m sure the filter was never cleaned. So, that’s what I’m going with. I removed the oil pump and checked that, and I’m going to flush the system a few times before i start it as well and a few times right after it start it to try to gent everything out, and then I will continue to keep a very close eye on things after that. If it continues to create shavings I’ll have to tear it down to bare cases to investigate deeper


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benroloff

Active Member
It is non-ferrous for the most part. Some globs of it did stick to a magnet, but consider that the rings that weren’t broken were very worn, so in theory there could be some ring material in there, and like I said I’m sure the po never cleaned the filter so it’s likely everything in there accumulated over years and years of wear and tear. Also once metal started getting into the oil I’m sure it started wearing on the trans and other misc bearings and bushings so I’m sure some of that is mixed in there, but since nothing is jumping out at me as really worn out I’m just gonna leave it for now. I’d love to tear this thing down to bare bones and do everything right from the ground up but apparently my parents think paying for stuff like college takes precedence over spending all my cash on rebuilding my motorcycle in the basement of their house…


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benroloff

Active Member
Worked on the e-ignition project a little more. Made a trigger out of an oil lite bushing and a high temp magnet. Just used a hand file to make the notches for the mechanical advance. Everything functions properly and the trigger activated the sensor just like it should.
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Also got an old Sun voltage gauge from my uncle that I found in an old box of parts, so I think I’ll mount that up to keep an eye on things, plus it’s a neat old gauge, I think it matches the bike nicely.

I lapped the intake valve today too as it was leaking a pretty good amount when I filled the intake port with brake clean. I know there are a lot of mixed opinions about valve lapping without also cutting the valve and seat, but I’m willing to take the risks for a better sealing valve. I opted to leave the exhaust valve alone since it isn’t leaking at all


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Maritime

Over 10,000 Posts
On these old Hondas you should just lap, sometimes cutting a new seat will remove all the hardened metal and then the valves beat the crap out of the head and it gets destroyed. It depends on the model, some are ok to cut, some not, so err on the side of caution and a good lapping is enough.
 

benroloff

Active Member
On these old Hondas you should just lap, sometimes cutting a new seat will remove all the hardened metal and then the valves beat the crap out of the head and it gets destroyed. It depends on the model, some are ok to cut, some not, so err on the side of caution and a good lapping is enough.

When people ask I’ll tell them this is why I only did a lap… make me sound all smart and stuff


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