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Discussion Starter #81
Ken, the plug was definitely oil-fouled. it smelled of gas as well, but oily. honestly, it sucks so much oil in i havent been able to run it long enough to get warm in that cylinder. it fouls before it even gets warm...

im sure youre right about inspecting pistons/rings and honing. i just havent done that before so im a little iffy. someone suggested relapping the valves myself, is that possible/advisable? anyway i probably will buy the athena engine gasket kit from oldbikebarn unless you have a better suggestion.

Jarrett
 

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one thing ive come across with the cm400 engine design is that the LEFT side is always screwed. always. yours is the fourth cm400 ive heard of with this problem. it looks good though. i have an 81 myself that i just put up in the projects forum.
 

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Discussion Starter #83
well for me its the right cylinder. still waiting on parts. oldbikebarn...then again i still havent actually cleaned the head yet. hopefully by the weekend, both will have happened.
 

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Discussion Starter #84
so i wanted to shoot out an update:

1. rebuilt the head with a used one from ebay. new valve seals, head gasket, everything nice and clean. kept my valves as they were in better shape. pulling valves is a pain in the ass. (pistons/rings/cylinder all looked really clean so i just cleaned the crowns and let it be)
2. made a rear tire hugger from thin sheet aluminum.
3. new petcock, also have a cx500d tank on the way. will try starting it up tomorrow with the new petcock in place.
4. after cleaning/painting the collector unit, put the stock exhaust back together.
5. got the wired sigma digital speedo-need to install.

anyway, im still working. still have a lot of things to work out. hopefully the motor is ok now. will let anyone who is actually reading this know how it goes.
 

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I'm not a real mechanic, but I've been reading forums for about 8 years now.

Anytime someone mentions a compression test, they are always reminded that the numbers are only valid if the engine is warmed up (as in good & hot), and the intake tracks are not blocked (either remove the carbs or block them open).

And use a tester that screws into the spark-plug hole, not the kind that you hold in place with your hand.

And a good, fresh battery, or other power supply.
 

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Discussion Starter #86
hey tom, thanks. i actually need to update this-i do have a running cycle now. peeing a little oil from the top, i think i just need to drain some off. i threw all the bits back together to ride it home from my buddys garage sunday night. anyway, ill keep the compression testing tips in mind.
 

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I agree with Ken, I've had several Honda twins. Tipicaly, they go about 15,000 miles then they need a new top end. Its not a poor design its just that most people thrash these little bikes, They can only last so long at 10,ooo rpm. My '71 cb450 had 912 miles when I got it, it was partialy seized up. I got it broke loose and it ran ok for a while but then it started to go sour like yours. I thought I could nurse it but it was actualy a exaust valve that had seized. I ruined the head!, by the time I finaly did the compresion test it was to late,save yourself a lot of time and grief and it will also cost less in the long run to fix it right.
 

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I agree with Ken, I've had several Honda twins. Tipicaly, they go about 15,000 miles then they need a new top end. Its not a poor design its just that most people thrash these little bikes, They can only last so long at 10,ooo rpm. My '71 cb450 had 912 miles when I got it, it was partialy seized up. I got it broke loose and it ran ok for a while but then it started to go sour like yours. I thought I could nurse it but it was actualy a exaust valve that had seized. I ruined the head!, by the time I finaly did the compresion test it was to late,save yourself a lot of time and grief and it will also cost less in the long run to fix it right.
 

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Discussion Starter #89
well. work has been slow. i moved from new mexico to missouri, my bike was still in nm with my wife for about 6 weeks while i was here. plus im back in school now. anyway--to sort things out for everyone, everything on the cycle works. motor is solid, shifts well, got a speedometer and tach on it, brakes are bled and working. tires have air. etc. so, having ridden it around for a week or two to be sure of my prognosis that all is well, i was convinced and tore it down for paint, this is something that i will pay someone to do next time. im just not getting the results i want. its ok, not great. thats all. im also getting a little sick of seeing this thing in pieces in the garage. but its getting very close now, and i thought id post a couple of photos. theyre poorly lit, the color is much better than that...







i also have a couple other bits painted, but still sanding/priming the tank, rear fender, and electrical spaghetti box...
 

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Discussion Starter #90
well. work has been slow. i moved from new mexico to missouri, my bike was still in nm with my wife for about 6 weeks while i was here. plus im back in school now. anyway--to sort things out for everyone, everything on the cycle works. motor is solid, shifts well, got a speedometer and tach on it, brakes are bled and working. tires have air. etc. so, having ridden it around for a week or two to be sure of my prognosis that all is well, i was convinced and tore it down for paint, this is something that i will pay someone to do next time. im just not getting the results i want. its ok, not great. thats all. im also getting a little sick of seeing this thing in pieces in the garage. but its getting very close now, and i thought id post a couple of photos. theyre poorly lit, the color is much better than that...







i also have a couple other bits painted, but still sanding/priming the tank, rear fender, and electrical spaghetti box...
 

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Discussion Starter #92
painting really sucks. esp without proper equipment--spray can in my garage with the door closed.

why spray paint? no compressor/paint gun
why in garage? best place i have
why with door closed and no ventilation? to keep dust/bugs out of my air (yes, i do end up sneezing/coughing/spitting yellow paint afterwards)

and on top of all that, it seems there is always a run, or a bug in the paint, or paint wrinkles because i forgot what day i painted what, or i suddenly realize my bondo job is shittier than i thought. so progress is slow. i will never do this again.

so anyway, some photos of the fuel tank-a little pinstripe goes a long way. not bad. not great either.










up close you see my lack of skill. now im just waiting on a couple of decals from a fellow board member, and we are go for clear coat!
 

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Discussion Starter #93
finally. the work is (mostly) done.

and here is the little yellow jerk...












still to come: rearsets, exhaust changes, new passenger pegs, maybe new shocks...

...seems to be smoking a lot on startup. so maybe more engine work, too. :( anyway, im riding it, and having a blast.
 

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Discussion Starter #95
well. ive been gone since retrotony burned out my eyeballs with his first offensive pic post. im not opening any threads started by that man anymore. the CM now has upgraded shocks (and a raised rear end), better electrical stuff (replaced fuse panel and some connexions), new emgo exhaust, rearsets. and here it is:









now if i could just get my carbs jetted properly...why oh why didnt i listen to geeto (et al)?
 

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Discussion Starter #98
Heh. I never got a straight answer about jetting and gave up. I just kept the choke on unless at idle. That worked real well, revved up to redline no problem, but obviously not ideal. It still wasn't much fun to ride, even at its go-fastiest, so I didn't keep it very long. Of course, unless your intake and exhaust mirrored mine, my numbers would be pretty much worthless.

The trick, as I understand it, is that these carbs are more precise than most and correspondingly more complicated. Simple jet swaps may improve conditions, but will likely not produce ideal results. For that, emulsion needs to change and probably the needle needs to be adjusted as well, except it isn't adjustable. It would be easier to use simpler carbs, like mikunis, but more expensive and probably more gas hungry.

Good luck. Sorry I can't be more help.
 

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Great job on the bike. I wish I could make my own tank too. The way I have it set up right now, I run out every 60 miles or so. How did you manage to raise the rear-end?

Do you happen to have the original side covers/panels?
 

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Great job on the bike. I wish I could make my own tank too. The way I have it set up right now, I run out every 60 miles or so. How did you manage to raise the rear-end?

Do you happen to have the original side covers/panels?
 
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