Camshaft Specs on Honda GX35?

Discussion in '4-Stroke Engines' started by JohnDN, Nov 18, 2008.

  1. JohnDN

    JohnDN New Member

    Here is a website for owner manuals and shop manuals for Honda Small engines.
    Go to Service>Service Information> and then choose owner or shop.

    Honda GX35
    I've gone through both the owner's manual and the shop manual and cannot find the camshaft duration, intake valve lift, exhaust valve lift, and camshaft timing. Does anyone know these specs? Or if anyone has this engine could they measure these specs?

    I ask because if you know these you can use calculators online to find the optimal intake runner length and optimal exhaust length. This will allow you to tune your engine's peak power toward the RPMs you will be running at. There isn't a lot you can do to tune a 4-stroke (not as much compared to a two-stroke) but I believe getting these numbers to calculate out the best intake and exhaust would be a very good step in the performance direction.

    If anyone can help out, I'd greatly appreciate it.

  2. Old Bob

    Old Bob Member

    I have full specs somewhere in my notes. Roughly: lift is .105-.112" both valves, intake duration 250 degrees.
    Given a few days I can find the information.

    It can be easily done by anyone also.

    Print out the free degree wheel at Tavia

    Take a free CD-ROM that we all get in the mail from AOL and size the tavia degree wheel to it, glue it on.Attach the CD-ROM degree wheel to crank add a pointer.
    The compression release needs to be disabled, remove cam and push a piece of paper towel into release mechanism in back of cam holding it in the retracted position.
    You can now check valve timing. a .001" or thinner peice of feeler stock can be used if you don't have a dial indicator to show opening and closing points.
    Measure actual lift with veneer.
  3. Silvaire

    Silvaire Member

    I don't have any specific info to offer you, but I am aware that model boat builders and racers are doing modifications to GX35 engines and are getting considerable increases in power. These include making new cams, using different carbs, and reworking the intake and ignition for starters.

    If you are interested in the potential of this engine you might try searching on some of the model airplane and model boat forums.
  4. Old Bob

    Old Bob Member

    Silvaire has a good suggestion. I came from RC and I'm familar with most of what has been done, I can give you links to the airplane forums where the Honda was discussed.
    Don't bother looking for the rc boat forums for information because I'm the guy you're looking for. :grin5:

    I found the cam specs.
    Measured duration @ adverised lift = .004"
    IO 10° BTDC
    IC 57° ABDC
    247° duration

    EO 48° BBDC
    EC 28° ATDC

    256° duration

    .106" lift

    38° overlap
    Last edited by a moderator: Dec 18, 2015
  5. MD Bob

    MD Bob New Member

    More GX35 Info?

    I would like to get more info on your work with the GX35 Honda. Any help would be great!
  6. Old Bob

    Old Bob Member

    Due to forums inability to enforce the sharing of accurate information and not censoring myth and lore, I have pulled all my tech info off the net and won't supply it to anyone.
    I've had people infringe on my copyrights of published material and images, claim my work as their own, attempt to copy my work by purchasing goods from me as a result I have ceased any support.
    Honda contacted me and was adament about support of any motor vehicle application and rightfully so with respect to liability.Offically Honda does not support or recommend the use of the M4 line of engines (this includes the GX22,GX31,GX25,GX35,GXH50,GXV50)
    for motor vehicle applications.
    I have since moved on to other projects and took the architecture of my proposed MB engine and expanded it to a 800cc twin cylinder engine for recreational vehicles. It produces in the neighborhood of 145 bhp/liter NA and only weighs 13 pounds more than 600cc two stroke twin in the same application.
    It gives up about 2-3 hp on the top end to the 600 but has low end torque that feels like a 900-1000 cc two stroke on the trail and about 3 times the fuel economy.
  7. MD Bob

    MD Bob New Member

    Thanks for your reply, and good luck with your new project!
  8. MD Bob

    MD Bob New Member

    Are there any performance parts for sale for the GX 35?

    Has anyone ever seen any Performance parts marketed for the GX 35? OLD BOB, have you ever seen any cams available? Has anyone ever tried cutting two lobes on the cam rather than one shared profile? Obviously it would shorten the life expectancy, but that is acceptable for competition engines. Thanks for any info on the GX 22/31 and 25/35 series engines.
  9. Old Bob

    Old Bob Member

    I made cams for them for a number of years.No buyers, so I stoppped making them.

    You don't need seperate profiles due to the geometry of the followers.I've done that, its not needed.
  10. MD Bob

    MD Bob New Member

    gx35 and other projects

    I would really like to talk with you. Is that possible?
  11. Old Bob

    Old Bob Member

    pm me here