Trail 90 wont turn over: help please!

Discussion in 'Old's Cool' started by Sidecar Jockey, Jul 17, 2014.

  1. lesman

    lesman Live easy, Brake Hard

    Joined:
    Sep 7, 2006
    Oddometer:
    736
    Location:
    Houston, Texas
    I"think" there are orings in or around the valve guide that tend to go bad with age.
    The bike will smoke if they aren't replaced.


    Les
    #21
  2. Sidecar Jockey

    Sidecar Jockey Been here awhile

    Joined:
    Aug 1, 2012
    Oddometer:
    651
    Location:
    MD
    Are these 'o-rings' in the valve guides like valve stem selas?

    I'll have to check into that, thanks. I wasnt planning on doing anything to the head, since my normal sized valve spring compressor is too big to use on this tiny head... but now I'll need to figure something out.


    The Dr ATV big bore piston (53.5 mm) didn't come with any info. I dropped the piston and cylinder off at the machine shop on Friday, and the machineist said that he will contact Dr ATV and get the boring specs. He quoted me $100 to bore the cylinder and fit the rings, which seems like a fair price.
    #22
  3. Cogswell

    Cogswell Spudly Adventurer

    Joined:
    Jan 3, 2005
    Oddometer:
    4,754
    Location:
    Riding with my pal Richard Cranium
    That price is high in my opinion. You should take him the head too and have him resurface the valves and seats. all included for $100 would be about fair.


    Mike
    #23
  4. Sidecar Jockey

    Sidecar Jockey Been here awhile

    Joined:
    Aug 1, 2012
    Oddometer:
    651
    Location:
    MD

    I wish. All of the machine shops in my area are crazy epensive. They all must be in on the price fixing together or something, because they all charge about the same price, do average work, and take a week too long to do it.

    I might try out one of those "mail me your cylinder and piston and i'll bore it" guys on Ebay next time...
    #24
  5. redprimo

    redprimo Been here awhile

    Joined:
    Jul 9, 2011
    Oddometer:
    571
    Location:
    central coast of California
    Your bike only has one valve guide seal on the exhaust, the intake valve dissent have a seal. If you get the Vesrah gasket set it is included. The oil seals for the kick starter, gear shift, primary shaft, cam shaft, or sub Trans shaft are not in the Vesrah set but dratv does sell them aa set. You really should make an effort to replace the valve guide seal. After 45 years it gets pretty brittle regardless of how many miles the bike has on it.

    I use a c clamp and a block of hard wood I made for that purpose to compress the springs. Not ideal but it works.
    #25
  6. ADVDucs33

    ADVDucs33 Adventurer

    Joined:
    Apr 11, 2012
    Oddometer:
    50
    Location:
    Western NY, sticks.

    If this seal were to crumble apart and go ca-puttz, would leaking fluids and loss of compression be the result? Like Sidecar, I think I have to tear into my little 90 as well.

    Thanks!
    #26
  7. Sidecar Jockey

    Sidecar Jockey Been here awhile

    Joined:
    Aug 1, 2012
    Oddometer:
    651
    Location:
    MD

    It would NOT cause an external leak or loss of compression. It would allow oil to get sucked down the valve stem and into the combustion chamber, resulting ain LOTS of blue amoke when the motor is running.

    The good news is that it takes me about 15 minuts to take the top end off of a trail 90. Its the easiest bike I have ever worked on.
    #27
  8. redprimo

    redprimo Been here awhile

    Joined:
    Jul 9, 2011
    Oddometer:
    571
    Location:
    central coast of California
    The valve guide seals rarely crumble. Usually the crack and leak but stay in place.

    The death of most of these engines is oil starvation of the top end due to a clogged oil screen or oil passage. Change the oil often and swap the 40+ year old clutch for a fresh one ( a 40 year old clutch is prone to disintegrating and creating lots of crud that clogs the oil screen) and you should have no problems getting 10-20k.
    #28