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1986 Rebel 450
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Discussion Starter · #61 ·
The oil filter was CLEAN. I just see glitter in the oil that doesn’t stick to a magnet. Not sure if I should just pull the head and cylinders just to have a look.
 

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1985, 86 CMX250C, 81 CM200T, 74 CL360, Invisible to cages, treat them accordingly. Avoids Road RAGE!
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@SoakedKarma

Why was each 450 Engine custom made?
Wasn't the Cmx 450 a regular bike, of course with a short production Time, Wich took the Engine from the already existing CB450 S?
I've often pondered that same thought???
I hope that either SK or another member can answer it.
Thanks for asking this!
 
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1986 Rebel 450
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Discussion Starter · #64 · (Edited)
A local shop that has been suggested by a few people around my way said they wouldn’t even touch it because it’s so old and hard to get parts for. Talked to a service guy there and he said it’s probably a crank bearing from the video. Didn’t even mention not having the carbs synched so I was alittle Leary about taking that advice. Jack also mentioned that the bottom ends rarely go bad on these engines. He said usually if they are bad it’s because of the starter clutch that would have to be replaced and that involves splitting the cases. So just getting a bottom end has a big gamble on it. Ugh. I hate this hamster wheel I’m on

I also hooked up a timing light and recorded a video on slow motion. I’m pretty sure the knocking happens at tdc

 

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It still sounds like a wrist pin to me due to the double knock at TDC.
 
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I always replace the gaskets when doing a head. It's false economy not to do so.
 
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1986 Rebel 450
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181 Posts
Discussion Starter · #68 ·
I drained the tank yesterday and put new fresh 89 fuel in the tank thinking it could be bad gas. Nope. Same problem. I bought a new cdi box from Jack last summer. Is it possible that the cdi box is maybe wonky and messing with the timing/pre detonation?

Also I talked to another mechanic for about 10 minutes at a shop. He also said it would be tough to work on with no parts available to get for that bike. Charges $119 an hour. He said just getting the engine off the bike would be close to 10 hours. 😂. That’s not even fixing the problem. So yeah. I don’t think it’s worth it. Unless I part out the bike I don’t want to tear open the engine and now have more problems if I try going down the selling it route. Ah my continued post is in my reply. Sorry it’s 5 am here and I’m still asleep
 

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CMX 250, 1996
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Mhhhh, I am no Mechanic and my skills there are nothing more than that of a average Person but I am pretty sure that it wouldn't take me 10 Hours to remove the Engine of such a bike.
This is something you could totally do by yourself, I think.
 

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1986 Rebel 450
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181 Posts
Discussion Starter · #70 ·
No definitely would not take that long. Maybe an hour if that. The engine I can remove. Fixing the problem that I don’t even know what to look for is the problem.
 

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1987 rebel 2004 sportster
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I am not a great mechanic so I would not attempt the engine rebuild. Good job thinking outside the box with the cm450 question. It takes me between 2 and 3 hours to do an engine swap on a 250- hard to believe the 450 would be much different. I can only tell you what I would do in your situation. I would find a rebel 450 that was in pieces or non-running and roll the dice on the engine being okay. I would use the best parts to make one good bike for myself and sell the remaining bike/parts. There is a 450 on craigslist in Troy NY asking $500. Another in VT asking $400 on FB market. Food for thought….
 

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1986 Rebel 450
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181 Posts
Discussion Starter · #73 ·
I took apart the top end today looking for what would be causing the knocking and to my pessimistic ways I have found nothing. Waste of time if you ask me. I think this may turn into a part out bike.

 

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It sounds like there's up & down play on the wrist pins, if I'm seeing what it looks like I'm seeing. There shouldn't be any.
The double knock ATDC would be clearly explained by this, if indeed there is vertical play at all on the pistons.
While it's open I'd definitely check the oil pump & all the delivery system that can be checked.
 

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Wonderful that you've found it!
Now to figure out how to fix it. ;)
 
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Discussion Starter · #80 ·
Exactly. I don’t think splitting the case is in my wheel house. No YouTube vids and my limited knowledge of this job will make it very tough for me. Shops around here won’t even look at the bike because it’s so old and no parts available. Unless I can find a bottom end/engine from eBay or fellow rebel 450 person . I think I’m sol
 
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