1966 Honda CM91 Restoration Project

Discussion in 'General' started by northvancpF, Dec 6, 2016.

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  1. Ponytail

    Ponytail Active Member

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    :77: I've been following your build thread regularly. I'm in total awe!!!
     
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  2. northvancpF

    northvancpF Member

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    auploads.tapatalk_cdn.com_20170128_f9fa86977bf66200b9c507fcf5fda091.jpg

    I doubled the shrink wrap.
     
    #62 northvancpF, Jan 28, 2017
    Last edited by a moderator: Jul 17, 2017
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  3. northvancpF

    northvancpF Member

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    auploads.tapatalk_cdn.com_20170128_229df5afb8e15c4d46b7aad7d582d1d9.jpg
    I don't think the speedo is correct. It was disconnected when I got it. Lol.
     
    #63 northvancpF, Jan 28, 2017
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  4. b52bombardier1

    b52bombardier1 Well-Known Member

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    Your electrical work is very nicely done and the bike looks awesome. I love it when somebody brings another old Honda bike back from the dead.

    Rick
     
  5. northvancpF

    northvancpF Member

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    Thanks! I actually took it out for a test ride on the weekend. Still not running correctly. The throttle cable is maybe stretched so I can't adjust out the slack. Making it hard to set the idle and air. Waiting for new cables to arrive.
    Also I could find 1st and 2nd gear but not third. I've adjusted the clutch a few times so not sure what's going on there just yet. Again, the idle is set too high, it doesn't want to stay put when in gear.
    So still some things to work out, but it starts first kick![emoji106]
     
    #65 northvancpF, Feb 1, 2017
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  6. northvancpF

    northvancpF Member

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    New rack from Thailand came today[emoji38]
    auploads.tapatalk_cdn.com_20170218_4e5cdc8e6ff7abc1c66391c7cbba202a.jpg
     
    #66 northvancpF, Feb 18, 2017
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  7. northvancpF

    northvancpF Member

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    auploads.tapatalk_cdn.com_20170218_9a10f690b969370490f6603fcff154a0.jpg
     
    #67 northvancpF, Feb 18, 2017
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  8. loopiemclooperson

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    Looks good and seems darn useful to boot!
     
    #68 loopiemclooperson, Feb 18, 2017
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  9. Ponytail

    Ponytail Active Member

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  10. northvancpF

    northvancpF Member

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    Hi guys. I need some help from smart guys who know about these bikes than I do[emoji3]. I'm getting close. I've got it running pretty well. Starts really easy. Idles. But still 'surges' low to high rev, making it hard to set the air and idle adjustment. That's one problem. The other is that it goes into gear, and shifts to second.... I think, but not third. Or it goes from neutral to second, then third, but not first?? Also, weird, the shifter will get 'stuck' and not return to position for some reason occasionally.
    Any thoughts?
    I've done so much work to this little bike but can figure out these couple issues. I've set the clutch adjustment a number of times so I don't think it's something simple. And with the fuel surge, I've cleaned and lined the fuel tank, new fuel lines, filters, cleaned the carb, gaskets, replaced the intake hose, new air filter... so it's all pretty new.
    Set timing, new oil, new battery, new rectifier.

    Any ideas? I want to put a plate on it and try it out[emoji3][emoji106]
     
    #70 northvancpF, Mar 28, 2017
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  11. b52bombardier1

    b52bombardier1 Well-Known Member

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    Shifting problems are often related to loose shift drum stoppers on these bikes. The roller arm on the stopper can also break or bend in a manner to no longer follow the valleys in the stopper plate.

    Rick
     
  12. northvancpF

    northvancpF Member

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    Hmmm. Thanks Rick. I'm not sure what any of those things are but they sound 'deep' inside. Time to do some research.
     
    #72 northvancpF, Mar 28, 2017
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  13. northvancpF

    northvancpF Member

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    Hi guys. Summer is here and I'm back working on the Hondas. I have my 1980 CT110 running like a champ, and I had the 1966 CM91 out today and I figured something out. Now I need help.

    I found 1st gear... but it's weird.
    Pull up once for 1st... push down once and you hit neutral. Push down again...and you're in second, press down again and you're in third...?

    Is that correct?

    Can't be.

    Anyone have an old CM91 who can tell me the shift pattern?
     
    #73 northvancpF, May 27, 2017
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  14. Fastestgrass

    Fastestgrass New Member

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    Hello. This is my first post here so hopefully i don't have too much trouble learning the format of this forum.

    Great looking CM91 you have. You've done a nice job. Yes, the 1 up, then one full down to neutral, and then 2 down is the normal shift pattern for the CM91. The owners manual recommends using 2nd and 3rd for normal riding, and the use of 1st gear for pulling out when riding with a passenger.

    If you don't mind, i've got a few questions that i hope someone can help me with. Maybe i will start a thread on my 1966 CM91 "resurrection" so i'm not hijacking this thread.

    It looks as though you may have had the cylinder off during your restoration and i was wondering if you have any good pictures of the cylinder studs. Someone had the cylinder off of mine and did bad things with silicone sealer at the base gasket and it looks as though they replaced one stud with what i'm guessing to be a stud from a CT110 or something as it is about an inch longer than the other 3 studs. I've seen some "A" and "B" studs available but i have no idea which one i need. According to the parts info on partzilla.com, the CM91 used 4 different studs, A,B,C, and D, while the CT90's of the day used 2 "A" studs and 2 "B" studs. I haven't found studs C or D available anywhere.

    I have a 69 CT90K1 that i can rob an A or B stud from it for now to get the CM91 back together, but i can't figure out which stud is which so i'm not even sure which studs i have and which one is missing. I know that the lower left stud should be one that has the full shank diameter just below the threads for the oil flow, but other than that i'm confused. The 11911-046-000 dust guard that is held on by the two lower studs is missing, and i'm assuming that because of the addition of the guard when compared to the CT90, the two lower studs would have been longer, hence the different "C" and "D" studs.

    In my google searches i've found past ebay auctions for the dust guard selling for like $80, but i found the part number listed on a lawnmower website selling for $8.77, but there was no picture of the item. I just took a gamble and ordered it anyway. I couldn't imagine that Honda would use the same exact part number over for a totally different part, but who knows. Maybe i scored an elusive, rare, hard to find dust guard dirt cheap, or i may have just purchased a lawnmower part that i can't use. If it is indeed a lawnmower part, i won't loose much sleep over the $8.77.

    I've read that the U.S. model of the CM91 had several differences than the rest of the CM91's sold all over the world. No "winkers", no "90" on the side covers, bobbed rear fender like the CT90, and there may be other differences. I was wondering if these differences is designated by the "A" in the vin number. My vin is CM91A-1112XX. Does yours just begin with CM91-1XXXXX? Was the cylinder originally black on yours, as mine is painted silver to match the side covers.

    Again, your bike looks great. Have you been able to get it running correctly or are you still having an issue? I hope someone here has an idea on my studs question. Thanks to all in advance for any help. I'll probably be posting a good bit here for awhile so please log in from time to time if you have a chance. Thanks.




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    #74 Fastestgrass, Jun 4, 2017
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  15. northvancpF

    northvancpF Member

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    Hello Fastestgrass.
    First off... thanks for the information on the shifting. That really sets my mind at ease. I was almost ready to take it into the Honda shop. I'm not a mechanic, just a hobbyist. Deep into gearing is probably too much for me.
    Sorry, I haven't had the cylinder off. It actually runs pretty well. I just removed the covers to clean and paint them and do the maintenance.
    My cylinder was silver too. I thought the previous owner may have just spray bombed it so I painted black to match my CT110, thinking that was correct.
    Here it is today, insured, pretty much ready to go. Still 'surging' making it difficult to set the idle. Otherwise, runs well.
    I need a new leg shield. I tried to patch, plastic weld the cracked one I have, but I'm not happy with it.
    Here's a picture of my 'winners' and the VIN. No 'A', I believe this is a Canadian release.
    Hope this helps. Let me know if I can help in any way with your project!
     
    #75 northvancpF, Jun 4, 2017
    Last edited by a moderator: Jul 17, 2017
  16. Fastestgrass

    Fastestgrass New Member

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    Thanks for the quick reply. Your hi-res pictures have already been a big help. I can see that the dust shield is held on by another nut, and not under the head nuts, so i believe i need another of the longer studs, even though the long stud that i have still seems excessively long for just the thickness of the dust shield and another nut.

    Your repair on the front side of leg shield looks very presentable, at least in the photo. I'd be interested to hear how you made the repair. I really like the rack. I need to get one. Is it from the ebay seller in Florida?

    I had an impossible time trying to dial in an idle also. While bumping the idle screw in and blipping the throttle to catch it before it would die, then adjusting the screw in more, and then blipping the throttle again, repeat--then it would just go in to an extreme rev, and i'd have to back the idle screw back out several turns and then the cycle would start all over again. After setting the ignition timing that was very retarded, it still would not idle. So i thought i would inspect the timing advance mechanism. I thought a sticky mechanism fit the senario, but found that the mechanism was fine.

    On my way back together i noticed on the points plate i could see where it had originally been set at one time. Then i noticed silicone sealer on the bottom side of the base gasket. Knowing that the silicone wasn't from the factory, i knew the cylinder had been off. I decided to check the valve timing and sure enough the cam was off by one tooth. So that's when i decided to do a full tear-down. When i go back together, i'm thinking the correct valve timing will be the cure for my idle issue. Does this sound similar to your idle issue?

    I can see from your pictures that they didn't bother to put the clamp back on the spark plug wire that attaches to a clutch cover screw and the clamp on the overflow tube at the cylinder stud. I'll have to start a thread on mine instead of rambling on about it here. Thanks again for the great pics and the quick reply.

    image.jpg
     
    #76 Fastestgrass, Jun 5, 2017
    Last edited: Jun 5, 2017
  17. Dezdan

    Dezdan Well-Known Member

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    Hey FastestGrass,

    I've done a bit of investigation over the years and came up with the same conclusions: the CM91A is different from the CM91 released elsewhere - No winkers/switch, no 90 label on the side covers, shorter rear fender, silver head, and possibly no leg shield (though I haven't been able to confirm that one yet). Mine is CM91A-127XXX and tracking down info on them has been fun! (n) None of the books nor wiring diagrams fit the CM91A, all fit the CM91 so trying to come up with what exactly this bike had has been a challenge. Currently I am working on a new wiring diagram for the 91A, just removing the winkers and correcting some wire colors, before I start a small run of harnesses. I'm hoping to start a full restoration later this spring. Does your 91A also have the manufacture date stamped above the wheel lock on the left side? Also, does your engine have a serial stamped in it, or is it blank?

    CM91A on the left, C105 on the right.
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