Vintage Dirt Racing on a 350 Honda Twin

Discussion in 'Racing' started by LC Garage, Jun 16, 2011.

  1. Chobro

    Chobro spinning the wheel

    Joined:
    Jan 29, 2004
    Oddometer:
    809
    Location:
    Albuquerque, NM
    Finally all caught up with this thread, good read.

    Is anyone aware of a good cheap coil option? My wires are crusty and plug caps are a loose fit. I went to remove the plug wires, but they are molded into the coils. I've got a set of airhead Bosch coils, not sure of they are a match ohms wise. Any help appreciated.

    How's that SL motor coming?
    :beer:
  2. LC Garage

    LC Garage On Any Sunday

    Joined:
    Mar 18, 2011
    Oddometer:
    793
    Location:
    Columbia County
    This post is titled priorities, because it always seems like I'm off on some tangent that doesn't relate to vintage dirt racing on a 350 Honda Twin. Two weeks ago, my daughter in the Air Force announced she was getting married during her Christmas leave, to her fiance....in Houston. Yikes. So with three weeks notice we are gearing up to fly to Texas and helping in any way possible to set up the wedding and make it all work out, and of course we will. As is typical, I'm juggling my duties as a parent, grandparent ( I have 4 grand-kids by my two other children) and of course a full time job, a shop with a bike being prepped for the 2013 MK1, my TTR250 prep for the D100 and of course the old SL350 that doesn't get half the attention I'd like to lavish upon it. Thus the title priorities, I do know how blessed I am, just saying that there is a lot competition for every waking hour. :D

    So this weekend (my last chance to do anything in the shop for a few weeks) I had three projects to prioritze; First was our recently purchased older Motor Home (this will be our "adventure vehicle" until one of us wins the lottery and we can buy a proper UniMog!), with a leaky roof and in temporary dry storage so this can be addressed. Second is the TTR250 because if I don't start riding pretty darn soon, I won't be worth a lick when it is time to race. In addition to the D100 on April 6, I've told Luke I'd like to hit at least one, maybe two OMRA events prior to the D100. Third was to try and squeeze some time in on the SL350, and to do all of these things while also working in going to a basketball game my oldest grandson was playing in. Whew! :lol3

    Working on the Motor Home roof, got one coat on all seams, need to do two more before we pull it out of storage;

    [​IMG]

    TTR250 thread can be found here;

    http://advrider.com/forums/showthread.php?t=654212&page=2

    This is the last photo of the day on this project, good progress being made;

    [​IMG]

    And a shot of the SL350 frame, with another possible fuel tank picked up off of ebay, I kind of like this one, but it will take some massaging to get it to fit;

    [​IMG]

    That's all for now, take care everyone! :D
  3. TwinDuro

    TwinDuro Befuddled Adventurer

    Joined:
    Jun 10, 2007
    Oddometer:
    364
    Location:
    Pac Nor-Wet, WA
    Oooh, very nice! Is that an MT250 tank Rick? It looks great on the SL.

  4. LC Garage

    LC Garage On Any Sunday

    Joined:
    Mar 18, 2011
    Oddometer:
    793
    Location:
    Columbia County
    At long last I'm back on the old twin, all the other projects are doing well:

    TTR is finished and rideable again;

    http://advrider.com/forums/showthread.php?t=654212&page=2

    Luke's MK1 bike is coming right along;

    http://www.advrider.com/forums/showthread.php?t=823952&page=21

    And the new (1986) race support vehicle, aka "Minnie Winnie" is progressing steadily, although I'm pretty sure we're going to have the pull the furnace to repair, but that is another story. Anyhow, with all these projects slowly coming together and the majority of my honey-do's somewhat under control, I had a whole day to devote just to the old SL350. :D

    This morning;
    [​IMG]

    Decided to use the tensioner arm on the left for the Polyamide sprocket and wheel upgrade, as the right hand one was in pretty good shape and can be used again on a non performance application;
    [​IMG]

    Drilling out original rivet that holds tensioner wheel in place;
    [​IMG]

    The center bushing from the original wheel must be used in the new wheel, note that the oil passages need to be aligned for proper lubrication of the needle bearing;
    [​IMG]

    Magic marker used to mark where oil passages line up;
    [​IMG]

    Swedged the rivet with tapered punch and then finished off with a brass drift;
    [​IMG]

    Cylinder cleaned and ready for honing;
    [​IMG]

    Cross hatch;
    [​IMG]

    Ring kit came from Greece and are universal 68mm, which require a lot of filing to work in 67mm bores. Because the quality of the rings is completely unknown, I opted for a pretty generous ring end gap. Starting from the top ring at .016, then the second ring at .12 and the oil ring at .010. The rings have no markings of any kind and the compression rings were completely symetrical, so without any position indicators, I just have to hope that they are going to work. :cry Note: these were the ONLY rings I could find that were even close to fitting the antique PowRoll big bore kit.
    [​IMG]

    All parts laid out: cleaned, honed, filed, etc. and ready for assembly (the long slender black lines to the left of the rings are the inner springs for the oil control rings, those had to be shortened as well);
    [​IMG]

    Heat gun was used to warm pistons for installation of wrist pins;
    [​IMG]

    First piston on, I quickly realized it would be a good idea to install the inner wrist pin clips before putting the pistons on the rods;
    [​IMG]

    Pistons and rings on and rebuilt tensioner in place, ready for cylinder;
    [​IMG]

    Note to self; no more multi-cylinder ring installations without proper ring compressors. Doing this alone and without the right tools was no fun and was lucky no rings were broken. Whew! :1drink
    [​IMG]

    Had figured on getting further then this today, but couldn't quit untiI the trick LameCo head was set in place, just to see how it looked. Yeah Baby!!! :evil
    [​IMG]

    One more shop session should have the motor buttoned up and then it will be on to the chassis. My old crew chief Randy has volunteered (insisted actually) to paint the frame, fuel tank and side covers, and if his past work is any indicator, it should look pretty sharp. Here is the my old 750 Norton that Randy helped build in 1975, he did all the paint and trim work on it;

    [​IMG]

    Stay tuned!
  5. Ladybug0048

    Ladybug0048 Bug Sister

    Joined:
    Nov 6, 2005
    Oddometer:
    11,538
    Location:
    Spokane Valley, WA (the dry side of the mountains)
    Nice to see you're getting a chance to work on your 350. :clap
  6. oregoncoast

    oregoncoast Racing Like a Noob

    Joined:
    May 15, 2007
    Oddometer:
    4,548
    Location:
    Duh!
    Very nice indeed!
  7. Loud Al

    Loud Al .

    Joined:
    Aug 16, 2005
    Oddometer:
    3,931
    Location:
    Forest Grove, OR
    Nice progress and a great shot
  8. Mr Fast

    Mr Fast Slowly striving

    Joined:
    Aug 21, 2005
    Oddometer:
    328
    Location:
    Flagstaff, AZ
    Rick,

    The SL350 motor looks great. Glad we could help. We'll miss you at the Mexican 1000 this year. Plan on being there next year! :rofl
  9. LC Garage

    LC Garage On Any Sunday

    Joined:
    Mar 18, 2011
    Oddometer:
    793
    Location:
    Columbia County
    Most definitely! :D
  10. LC Garage

    LC Garage On Any Sunday

    Joined:
    Mar 18, 2011
    Oddometer:
    793
    Location:
    Columbia County
    Today's mission was to get the chassis, tank and side panels ready for Randy, so he can take them to his shop, paint 'em up and make them pretty! :lol3

    Frame with MT250 tank and home-made side panels that came from the old parts bike;
    [​IMG]

    Factory tank locators are in the way;
    [​IMG]

    A quick cut with angle grinder and cutting wheel (ground off flush later);
    [​IMG]

    Dropped old tank on and took a quick measurement, wanted to make sure the new tank wasn't going to ride too low and hit the motor;
    [​IMG]

    New tank, just high enough so when dropped into final location should clear motor just fine;
    [​IMG]

    Another quick mock up just to see how it all fits, before getting out the torch and hammer;
    [​IMG]

    Frame was a bit wide at the top;
    [​IMG]

    [​IMG]

    [​IMG]

    No problem!
    [​IMG]

    [​IMG]

    Lots of heat and a big hammer!
    [​IMG]

    While the frame cooled, decided to clean some motor parts. These old gaskets are really stubborn! :eek1
    [​IMG]

    [​IMG]

    After the frame cooled, mocked everything up one more time, looking good! :D
    [​IMG]
  11. LC Garage

    LC Garage On Any Sunday

    Joined:
    Mar 18, 2011
    Oddometer:
    793
    Location:
    Columbia County
    When I left off on the motor, the cylinder was installed, but the head, rocker box and cover were just mocked into place;
    [​IMG]

    After taking it back down to the cylinder and carefully rechecking all details, reassembled and used spray copper-coat on all gaskets. For cam installation I wanted the head and cylinder firmly in place, so used the outer perimeter studs and nuts to hold them down. With head and rocker box installed, time to slip the cam into place, but first the sprocket has to be slipped into place (the t-handle is there just in case I dropped the chain before getting it wrapped around the sprocket);
    [​IMG]

    Now the cam, but which one? Because these motors were already a hodge-podge of parts, a little measuring might reveal one of the cams with a little more lift;
    [​IMG]

    Cam #1 @ 1.44"
    [​IMG]

    Cam #2 @ 1.54", bingo!
    [​IMG]

    Ruh Roh! The bigger fatter camshaft did not want to go throught the sprocket without hanging up on the bottom of the rocker box. After several tries and even a rest break, I decided to try Cam #1. It went in like a hot knife through warm butter. Grrrrr. So here is where is I stopped for the day;
    [​IMG]

    At this point I looked at the cam sprockets to see if one of them had a bigger opening then the other, but on first glance they appear the same, and also have the same part number. I did a bit of reading on the internet and there is some chatter about high lift cams requiring different sprockets, so I'll have to explore that option. I also considered grinding a small relief in the bottom of the rocker box to allow the cam snout to pass, but first I'll check in with CB350 racing guru Mr Fast and see what advice he might have. :cry
  12. LC Garage

    LC Garage On Any Sunday

    Joined:
    Mar 18, 2011
    Oddometer:
    793
    Location:
    Columbia County
    Mr Fast came through (:thumb), here is what he said;

    "Talked to Owen and as I suspected he had to auger out the opening where you insert the cam into the rocker box to get the high lift cam to fit. Interestingly, after inserting the cam he had to grind down a ridge in the rocker box so the cam could spin! Make sure yours will turn over after you get it fitted."

    After receiving the information from Mr Fast, I did some further research on the inter-web and came up with this build thread, from another CB350 roadracer;

    http://www.sundialmotosports.com/hondacb350.htm

    And his quote (from the engine portion of his commentary);

    "You will need to clean out the entrance for the cam in the cam box so the redesigned cam lobes will fit. You will also need to clean the ridges off the cam box floor and enlarge the opening in the cam sprocket. That's all you need to do fit the new cam."

    So time to get out the grinder and make a little more room! :lol3
  13. oregoncoast

    oregoncoast Racing Like a Noob

    Joined:
    May 15, 2007
    Oddometer:
    4,548
    Location:
    Duh!
    Sure. What's the worst that could happen....

    :lurk
  14. LC Garage

    LC Garage On Any Sunday

    Joined:
    Mar 18, 2011
    Oddometer:
    793
    Location:
    Columbia County
    And this from the hondatwins.net site;

    "'68 - '70 had the fat cam
    '71 - '73 had the thin cam

    all parts are interchangeable between CB and CL for the same years (68 - 70, or 71 - 73)
    you MUST use the cam and rockers for the correct years (either fat or thin cam)

    the cam boxes can be used between the fat and thin cams but you will have to remove a little material to allow the cam to slide through.

    all other parts are interchangeable"
  15. LC Garage

    LC Garage On Any Sunday

    Joined:
    Mar 18, 2011
    Oddometer:
    793
    Location:
    Columbia County
    Armed with the knowledge that grinding is the accepted pratice to get the larger cam installed, I pulled the rocker box off and set to work. First marking the offending areas (Note: as Mr Fast warned, there were witness marks where the large cam had been rubbing on the floor of the rocker box). So not only would material need to be removed from the vertical ridge to allow the cam to slide thru, but also from the ribbing on the floor;

    [​IMG]

    [​IMG]

    Dremel;
    [​IMG]

    Removed just enough material to get the job done;
    [​IMG]

    Now the cam fits;
    [​IMG]

    Checking thru two sets of rocker arms, not one of them had the 286 casting number that many say are correct for the larger cam, so will be doing more research before proceeding. Still it was sure nice to see the cam sitting in place! :D
  16. Mr Fast

    Mr Fast Slowly striving

    Joined:
    Aug 21, 2005
    Oddometer:
    328
    Location:
    Flagstaff, AZ
    Rick,
    On the higher rpm engine builds you also have to shim the rocker arms so they don't hit each other. The rocker arms you have should work fine. On road race engines they actual lighten them. If you want, sand them smooth & get rid of any casting lines as it will strengthen them.
  17. LC Garage

    LC Garage On Any Sunday

    Joined:
    Mar 18, 2011
    Oddometer:
    793
    Location:
    Columbia County
    So time to get out the grinder and make a little more room!

    :rofl

    Fixed

    Ahhh..the magic word "Grind"...now I'm happy! :lol3

    And stay tuned, because as soon as the motor is together and the frame leaves for the paint shop, all the little chassis tid-bits laying around the shop are going to get drilled! :evil
  18. Loud Al

    Loud Al .

    Joined:
    Aug 16, 2005
    Oddometer:
    3,931
    Location:
    Forest Grove, OR
    Think how much lighter that will make the bike


    :hide
  19. oregoncoast

    oregoncoast Racing Like a Noob

    Joined:
    May 15, 2007
    Oddometer:
    4,548
    Location:
    Duh!


    [​IMG]


    :lol3

    In one thread, I've got a friend doing everything he can to lighten his dirt bike by removing important frame parts and drilling holes everywhere.

    In another thread, I've got a friend building the heaviest dirt bike known to mankind and adding metal to metal to metal. :deal

    That sad part is....they are both doing it in the same damn garage!

    I'm wondering if Luke isn't just adding the metal that Rick is cutting off.....


    :1drink
  20. TwinDuro

    TwinDuro Befuddled Adventurer

    Joined:
    Jun 10, 2007
    Oddometer:
    364
    Location:
    Pac Nor-Wet, WA

    Only Danny knows for sure...
    :augie