74/75 Montesa Cota 247... Simple? fixes

Discussion in 'Trials' started by Buschog, Sep 20, 2016.

  1. Buschog

    Buschog Been here awhile

    Joined:
    Nov 13, 2015
    Oddometer:
    921
    Location:
    Carson City, NV
    I bought this last week because I want to try out trials. $400 for a running bike was too hard to pass up. It's obviously not pristine, but then... Neither am I.

    [​IMG]


    I hope to get some time on the pegs over next few weeks. There is an event (with a vintage class) with SACTOPITS in October that I'd like to compete in. In order to do that, I need to make some repairs.

    I need to order a gas cap. I doubt the organizers will allow me out on the loop with a sock stuffed in the gas tank.
    I also need to fit a spark arrestor. I've never seen a silencer like the one on this bike. Any info on it would be great.

    [​IMG]

    Anyway, I pulled the amplifier, er silencer off last night to get a look inside.

    [​IMG]

    Packed with carbon and unburned oil. The baffle was completely plugged. All of the little holes were clogged, so I essentially had a straight pipe. After disassembly, I scrubbed on all of the parts for the better part of 3 hours, then let the baffle soak in denatured alcohol (it's all I had) over night.

    I still have some carbon to scrape off before I put it back together. Can I get a "universal" spark arrestor to fit? Do the supertrap style disks act as an arrestor?

    What fuel/oil ratio do I want to run in this motor? Whatever was being used is less than efficient. Should I be looking at jetting or something else? All thoughts are welcome.

    My plan is to just ride it, but I have to get it rideable first. I may at some point attempt a restoration but that time is not right now.
    #1
    spokester likes this.
  2. lineaway

    lineaway Long timer

    Joined:
    Oct 1, 2011
    Oddometer:
    8,746
    Location:
    nm
    That is a supertrap spark arrestor with a quiet tp. Should be able ti get a cap from inmotion. I gave you a link in the first thread .
    #2
  3. Buschog

    Buschog Been here awhile

    Joined:
    Nov 13, 2015
    Oddometer:
    921
    Location:
    Carson City, NV
    Yup can definitely get the cap from inmotion. They have the best price too. Thanks for the link
    #3
  4. Brewtus

    Brewtus Buffoonery, Inc.

    Joined:
    Jul 30, 2008
    Oddometer:
    5,457
    Location:
    Portales, New Mexico
    Damn good thing you snapped it up, or I would have. You are further ahead of the game than you think. I would compete on that Montesa right now, but then again I'm not right in the head... :lol3
    #4
    Grooster likes this.
  5. Buschog

    Buschog Been here awhile

    Joined:
    Nov 13, 2015
    Oddometer:
    921
    Location:
    Carson City, NV
    I'd just like to get some time on it before I commit 100% that I'll compete. I ordered the gas cap from inmotiontrials the other day. It should be here by next week some time. I cleaned and repacked the exhaust the other night and it's way quieter. I have an exhaustive leak between the mid-pipe and silencer. Hopefully some high temperature rtv will cure that.

    Gonna try to get out on it over the next few nights for some slow balance exercises, but that pesky job keeps getting in the way. I'll definitely ride over the weekend, and my wife wants for us to get the big bikes out and go for a ride.
    #5
  6. Grooster

    Grooster Face Plant Specialist

    Joined:
    Jun 20, 2011
    Oddometer:
    215
    Location:
    Wichita, Kansas
    Add a inline fuel filter, too. That was my big mistake after thinking I had the TL125 tank cleaned out properly (I did not). I couldn't figure out why it would run well then cough on me in the middle of a section. I still had crap in the tank that was making its way into the freshly rebuilt carb. Taking the time to coat the inside of the tank AND adding a fuel filter eliminates a lot of frustration later. The rest should be simple maintenance. You're going to love this bike...
    #6
    lineaway likes this.
  7. LowPSI

    LowPSI Been here awhile

    Joined:
    Jan 19, 2010
    Oddometer:
    585
    Location:
    California
    Like Brewtus said $400 is a steal. The Cota 247 is bulletproof. Montesa sold over 30k of them. I rode, now I restore 'em. With just a bit of work you will have a fine vintage bike. You best source for new parts is www.southwestmontesa.com .

    A few basic suggestions that are low cost: I would trim that silencer bracket down before you hook yourself on it. Check/replace the foam air filter element. Flush out the tank, clean the carb, don't over tighten the carb manifold it will warp the carb and cause the throttle/slide stick open. New tires will make a huge difference. If you don't want to spring $$ for them look for some used take off's from a club member. 90 wt gear oil in the gear box, ATF in the clutch. 5 wt fork oil.

    If some day you decide to restore it you will find that it's simplicity make it a joy to work on.

    I think I know this bike. I think the original owner was a rider/artist from San Diego named Mark Lueck. He was a custom helmet and bike painter.

    and one final thing please.....only one "S" in Montesa. :-)
    #7
  8. Buschog

    Buschog Been here awhile

    Joined:
    Nov 13, 2015
    Oddometer:
    921
    Location:
    Carson City, NV
    I'll have to look at the inside of the tank. It already has an inline filter. Maybe I'll call the po and ask if he coated the tank. He did say they had been riding it a little, here and there, for the last couple years.
    #8
    Grooster likes this.
  9. Buschog

    Buschog Been here awhile

    Joined:
    Nov 13, 2015
    Oddometer:
    921
    Location:
    Carson City, NV
    I'll check the painters sig on the tank. I think Bill? I was told the original owner was from Fallon, NV. But your artist rider friend could have painted it. The PO was a mx racer back in the day and said the guy that used to do his helmets also did the bike for the original owner. I'm only the third owner.

    The welding job on the bracket and mounting point are atroscious. Both will get prettied up over the cold months. That and all of the maintenance.

    I keep going back and forth in my mind about a restoration. If I love it after a few rides that will probably happen.
    #9
  10. motobene

    motobene Motoing for 46 years

    Joined:
    Mar 9, 2013
    Oddometer:
    5,310
    Location:
    Wichita Mountains SW Oklahoma
    Fun project!
    #10
  11. Buschog

    Buschog Been here awhile

    Joined:
    Nov 13, 2015
    Oddometer:
    921
    Location:
    Carson City, NV
    Are there any project/build threads of these bikes? I've seen a couple not taken to completion but that's it.

    Course I haven't looked real hard either.
    #11
  12. Buschog

    Buschog Been here awhile

    Joined:
    Nov 13, 2015
    Oddometer:
    921
    Location:
    Carson City, NV
    I was close, not really. The painter was Hill.

    Ring a Bill er bell?
    #12
  13. sdm

    sdm Adventurer

    Joined:
    Mar 23, 2005
    Oddometer:
    46
    Location:
    Surprize Valley Cal.
    Nice bike and a good starting point for a resto. Mat at Speed & Sport also has parts and shows a gas cap on his web site for that. I have a 74 I am competing on in AHRMA NW events and it is a fun bike. Bushey Ranch Cross Country , trial and MX 10/1 & 10/2 are this weekend and is always a great venue if you want to try it out some vintage trials etc. I have a FMF silencer spark arrestor on mine and it works well.
    Sam
    #13
  14. Buschog

    Buschog Been here awhile

    Joined:
    Nov 13, 2015
    Oddometer:
    921
    Location:
    Carson City, NV
    Poor bike has just been sitting in the garage. I've done some balance practice but that's it. The last 2 weekends have been booked solid. Hopefully I'll be granted some time soon to try actually riding it.
    #14
  15. Grooster

    Grooster Face Plant Specialist

    Joined:
    Jun 20, 2011
    Oddometer:
    215
    Location:
    Wichita, Kansas
    Don't discount the balance practice when you don't have time for much else. Dead engine balance practice is helpful even for 15 minutes a day.
    #15
    Buschog likes this.
  16. Buschog

    Buschog Been here awhile

    Joined:
    Nov 13, 2015
    Oddometer:
    921
    Location:
    Carson City, NV
    So far 1.5 seconds on the pegs is good balance. I have MUCH work to do.
    #16
  17. lineaway

    lineaway Long timer

    Joined:
    Oct 1, 2011
    Oddometer:
    8,746
    Location:
    nm
    Concrete or in the dirt.
    #17
  18. Buschog

    Buschog Been here awhile

    Joined:
    Nov 13, 2015
    Oddometer:
    921
    Location:
    Carson City, NV
    Smooth Concrete. I need to roll is out into the crushed gravel backyard to get better practice.
    #18
  19. Buschog

    Buschog Been here awhile

    Joined:
    Nov 13, 2015
    Oddometer:
    921
    Location:
    Carson City, NV
    How hard is it to replace fork seals, tear down and inspection stuff? Never done it. Forks are leaking and sticky in compression and rebound.
    #19
  20. gearheadE30

    gearheadE30 @LC8Adventures

    Joined:
    Jan 20, 2012
    Oddometer:
    1,873
    Location:
    Indiana
    I personally find smooth concrete to be more difficult than 'off road' surfaces, for some reason. My balance isn't great, though.

    Fork seals aren't too bad. The hardest part can be getting the bolts out of the bottom of the damper rods - they're the two socket head cap screws on the bottom of each fork leg. The part they thread into will want to spin inside the fork. Usually an impact gun can work well to get these out, and they are easiest to break free when the springs are still in the fork because it puts some friction load on that damper rod to keep it from spinning. Just don't remove the bolt all the way with the spring still in. I'm not familiar with that bike specifically, but the end of the damper rod often has a female hex in it which, in the absence of a large allen driver, can sometimes be grabbed with a broom handle or other piece of wood run down through the fork tube.

    I've probably made it sound worse than it is, but here's my order of operations. Remove forks from the bike. Try to break the damping rod bolts loose at the bottom of the fork legs. If they come, great. If not, there are other ways. Unscrew the fork caps and remove any spacers and the springs. Invert the forks and drain the oil out. Now, completely remove the damper rod bolts. Your dust caps above the fork seals are already missing, but normally I would slide those up, and then remove the internal snap ring above the fork seals. Now, clamp the lower fork legs in a vise carefully but firmly. Slide the upper fork tube all the way in, and then yank it out. This will eventually pop the fork seals out, and boom, it's all apart. Check for gouges in the tubes, replace the bushings and seals (the bushings will almost definitely be worn in my experience, and new ones will feel great), and assembly is pretty much the reverse of disassembly. It sounds worse than it is, and there are a bunch of great DIYs out there if my abbreviated methods aren't all that clear.

    A random picture of the guts of a damping rod fork:

    [​IMG]

    Love the project! I always enjoy seeing people bring these old bikes back to life.
    #20
    spokester likes this.