building my motor up-need help

Discussion in 'High Performance Bicycle Engine Tips and Motorized' started by brywink04, Jan 22, 2016.

  1. sbest

    sbest Member

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    What did you do with the beer? <stupid question>
    Here is a beer as a necessary adjunct to CC'ing a head:
    [​IMG]

    It is a fine home crafted ale made from true malted barley and hops.
    Absolutely nothing to do with the CC'ing process of course...

    I don't have a great problem getting the NT carb to seal, even without the "O"ring or sealer.

    Use the "O"ring and push the carb on tight or use a TINY amount of RTV or 3Bond or YAMABOND sealer.

    RTV silicon is not really gas resistant, but it will work.
    This stuff is the BOMB! <now investigated by Homeland Security>
    If you have to seal cases of flat metal to metal surfaces. Yamabond is same stuff.
    [​IMG]
    Gas resistant and holds quite firm. Used to seal all motorcycle cases that do not use gaskets.
    The number doesn't seem to matter much, more about package size, but look it up.
    A little goes a long way.

    A KTM 85 SX is an awesome piece of kit!
    The only reason for anything bigger is if you are too tall and heavy.
    With both the 125 and the 300, I like the 125 more. The 300 is a brute, the 125 a Thoroughbred.
    Mine are set up for woods too. Soft shocks and tires, heavy flywheels and broad powerband pipes.
    I have a 125 SX motor set up for road racing. Peaky with harsh acceleration for high speed pavement stuff.
    Those KTMs can do it all.

    So, all those guys riding big bikes are compensating for something...
    I ride a small bike, because I am comfortable with my inadequacies...

    I am glad all you guys understand.

    Steve
     
    #21 sbest, Jan 25, 2016
    Last edited: Jan 25, 2016
  2. 2door

    2door Moderator
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    I have seen a couple of NT carbs that the slots were cut too deep and allowed an air (vacuum) leak unless those slots were filled. I've had good luck with a product called 'Seal-All'. It is one of the few that is gasoline resistant. Most silicone sealers are not. Read the label. Most will say "Not compatible with gasoline".

    I've never tried Steve's Yamabond but it is probably close to the same product.

    The 'O' ring idea is okay but the carb must be pressed tight against it and held there while tightening the clamp or it will not seal.

    It's also a good idea to roughen up the surface of the intake manifold a little with sandpaper so whatever you use to seal can get a grip. The chrome plated steel manifolds don't seal as well as the older aluminum manifolds.

    Another area to look at is the flange where the manifold attaches to the cylinder. The steel manifolds are notorious for having a warp due to the welding process and the flange isn't as flat as it should be for a good gasket surface. It needs to be 'lapped' to make it flat.


    As far as using beer to CC a combustion chamber; You can but I can only hope you use cheap beer. Coors would be a good choice here.

    Tom
     
    #22 2door, Jan 25, 2016
    Last edited: Jan 25, 2016
  3. brywink04

    brywink04 New Member

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    dont mean to bring back an old post but,

    i have about a 160 miles on my bike. and so far ive done the following
    -cleaned ports
    -resurfaced head
    -same exhaust as previous
    -gt80 reed valve
    -keihin 16mm carby
    -sbp shift kit

    so i curious if i should port match the intake to the reed valve block, and what spark plug should i use. also what oil ration should i go with? and anything else i should think about? i bought this carb and reed valve set up because the motor was running way to rich and was flooding out the airfilter thanks
     
  4. sbest

    sbest Member

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    It is normal for piston port engine to spit fuel back into the air filter. Weird huh?
    Nature of the beast.

    Personally, I'm having great luck without a reed valve so I haven't tried on the bike engine yet. I do have huge experience with reeds on the KTM and Yamaha Blaster / DT200.

    If you are using a reed valve, you should have the piston skirt drilled to let more air flow. The standard advice with reed valves is to port match everything. The goal is to have a near constant cross-sectional area from filter box to carb to cylinder window with gradual area increases (trumpet or venturi) at both ends. Set the reed as close to the crankcase as you can and the carb as close to the reed as possible. Ideally the intake port into the crankcase will be the cross-sectional area as the carb thru the entire stroke.

    I'm using 32:1 with good synthetic oil and happy with that. Seals well, enough oil and not too messy.

    With only 160 miles on, your engine is hardly broken in yet. It will get more power as you put 3-4 tanks of fuel thru it. I am putting 20-100 kms a day on mine, love it!

    Steve
     
  5. brywink04

    brywink04 New Member

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    okay thanks, ill run it some more. this is my 2nd tank on the bike.
     
  6. brywink04

    brywink04 New Member

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    okay, so i got the reed valves on the bike and it now has a little over 200 miles on it. I noticed that the reed valves have made it a little leaner so its running perfect now but i have less rpm. but more torque.i also noticed that i have a blown base gasket? so pulled the head off it and found some pretty bad scoring in the cylinder... im running 16-1 oil with honda synthetic pre mix oil on 91 pump gas. and im running a br8hs plug i beleive. i noticed the scaring when i surfaced the head and top of cylinder, but it was not this bad. im assuming soft cylinder? i will hone the cylider and reinstall a base gasket. lastly i know this isnt a lean issue according to the plug it is running a little on the ritch side. and im also curious what the spacer was for that came with the reed block. can i remove that to move the reeds closer to the cylinder? the kit i have is the gt80 reed valves with keihin 16mm
    thanks
     
  7. sbest

    sbest Member

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    I don't believe you are going to be able to hone the streaking out. I would not try to hone it.
    I had that happen on my first cylinder and blamed it on the poor air cleaner. I ran that cylinder a long time with no problems (and a better air cleaner!). Are you using a piston with the intake skirt drilled for the reed valve?

    Steve
     
  8. mike carter 2

    mike carter 2 Member

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    i removed the spacer. got better throttle responce
     
  9. brywink04

    brywink04 New Member

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    what i have done, i removed the spacer behind the reed valves, the piston skirt already is opening the port all the way(not covering any intake port at tdc), mild porting, port matched as best i could everything, head is also milled down. but now my bike is ascting as though the octane rating is too low, (pingy, sluggish) im running about 190 psi compression cold, at 32-1 oil and have about 250 miles on it. i did not drill holes in the piston because i am unsure on where i should drill them, the amount of holes, and the size hole to drill, another thing i was thinking i that the pipe i have on it is not working with the set up i have.
     

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