preventing power loss

Discussion in 'Performance Mods' started by jaguar, Jan 12, 2013.

  1. jaguar

    jaguar Well-Known Member

    If you have a head gasket leak (due to uneven head or cylinder top surface) or a crankcase leak then you will have power loss. Using sandpaper on top of glass you can easily plane the head and cylinder top.
    How to check for crankshaft seal leaks
    Remove the spark plug and magneto. Put water and about 10-20% dishwashing liquid soap in a spray bottle. Spray the left crank seal and push the bike forward and rearward so that the descending piston creates a momentary crank pressure. If there is a seal leak then it will blow soap bubbles. If the leak is big then it wont blow a bubble and you will have to listen for escaping air.
    Put the magneto back on and remove the stator coil. Remove the primary drive gear. Spray the right crankshaft seal and turn the engine over by turning the magneto. It is possible also to put an electric drill onto the left crankshaft to turn the engine over. Turning it by hand is hard to do fast enough.
    Both seals can be replaced by prying them out with a jewelers screwdriver and pressing the new ones in by hand after putting engine oil on the inner parts of the seal and also the exterior of it where it will be contacting the crankcase. You should have someone move the crankshaft CW and CCW by moving the magneto while installing the right seal. That is because there is a lip on the shaft that the seal sometimes will not go over. Best seals are available from Rock Solid Engines in Australia.
    AS an alternative to turning the engine over while looking for bubbles you can have more internal pressure in a continuous way by sealing the exhaust and intake (only if no reed valve is installed) while the piston is at or near dead bottom. The exhaust port plate should have a motorcycle inner tube stem in the middle of it so you can use your air pump to pressurize the crank. I did this for a better idea of how much the seal was leaking after seeing some small bubbles doing it the easy way. I made the exhaust plate out of wood and I sealed it with silicone sealant. Here is a picture of it;

  2. Fabian

    Fabian Well-Known Member

    That's a really smart and switched on idea. :idea:
  3. Fabian

    Fabian Well-Known Member

    Pressure testing the crankshaft seals will forever now be nothing more than a 5 minute job
  4. jaguar

    jaguar Well-Known Member

    I am in the process of using sealed crankshaft bearings as a first line seal. Last night I put it together and doing a pressure test now I see soap bubbles escaping from around the bearings. So I will split the cases again and move the bearings inward a bit and put Goop around the area that they will be pressed back onto so there will be a good seal. I'm hoping for a 100% seal since the seals I have are shot and I'm waiting for some more to arrive. Once my low psi pressure gauge arrives I can test for crank pressure to know exactly what the ratio is. I don't want it to be more than 1.5:1
  5. BigBlue

    BigBlue Active Member

  6. jaguar

    jaguar Well-Known Member

    yeah, of course, metal is better but I thought I'd try the wood to see if it would work and it did.
    Today is a marathon day for engine repair. It is still leaking after using the Goop. I will tear it down again and use something else this time.
    [1 hour later]
    With time to eat lunch and think about it (instead of tearing into it again), I don't think the Goop was that ineffective. The bearing seals are a hard type of rubber and not designed to seal perfectly. It's either that or I damaged them when prying them off in order to stuff the bearing with Badfish grease. So I consider this a failed experiment. Oh well, you don't know until you try. I will put my barely functioning seals back on and wait for the new ones from Rock Solid.
    Last edited: Jan 13, 2013
  7. jaguar

    jaguar Well-Known Member

    I forgot to mention that I found there was excess resistance in the clutch shaft bearings which was discernable just by turning the shaft by hand (after I removed the chain and clutch) On the sprocket side bearing I had to use my exacto knife to pry the seal off with the sprocket in place since I couldn't remove it. So I couldn't get as much BADFISH GREASE in there as I'd like but it's extra lubricating properties hopefully will make up for that. With both bearings greased the shaft turned much easier. People don't realize that a little turning resistance anywhere from crankshaft to rear wheel robs a big percentage of power when the engine is of small displacement.
  8. geebt48cc

    geebt48cc Member

    Of the 760 miles I've got now on the HT 66cc, 450 of those has been without a head gasket. I've done all kinds of mods, which includes milling,porting,reed,etc-- without using head gasket. Bike runs very strong without any signs of leaks. After reading this, I just wonder though? I can tell a small bit, that after riding a few miles with getting engine to temp, that maybe the engine isn't quite as strong as it was first mile. It's so close to beingthe same, that maybe it's just me???

    Once again though, I do
    keep everything torqued down, and it shows zero leaks?
  9. jaguar

    jaguar Well-Known Member

    Almost every time I take mine apart I resurface the head and the cylinder mating surface and yet I still get leaks as is evident by the oil on the cylinder fins. A good design allows compensation for the mating surfaces to distort due to unequal heating (due to most of the heat at the exhaust side). I may make a head gasket out of fibrous gasket material. I've also toyed with the idea of grooving the head and cylinder to accept an o-ring. A lot of motocross engines have o-rings.
  10. Purple Haze

    Purple Haze Active Member

    I have been considering o-ringing, also. One more thing to point out concerning leaks, the sparkplug mounting surface was not flat on my last engine, luckily I work at a machine shop with a flycutter, otherwise I wouldn't know how to true it up. Finally, I've had sparkplugs that had a bad sealing ring on them.
  11. Fabian

    Fabian Well-Known Member

    Since i've been using the CR Machine Man billet twin spark plug cylinder head, i haven't had a single oil leak from the cylinder head and mating surface; not a single itty-bitty little leak.

    I'm telling everyone right now: just hit up the credit card for a CR Machine Manufacturing billet twin spark plug cylinder head, not just because it gives a perfect cylinder head gasket seal, but because it's the dang coolest looking billet cylinder head out there !!!
    Last edited: Jan 18, 2013
  12. jaguar

    jaguar Well-Known Member

    Is there a web address for the head?
  13. Fabian

    Fabian Well-Known Member

    There certainly is, and the head is available in three versions: medium compression and high compression and with the optional provision of a screw-in decompression port, which is the same thread and depth as the other spark plug holes.

    I have no idea why his eBay store is no longer on the site but JN Motors has his Twin Spark Plug cylinder head (without decompression port), but no information is given if it's the medium or high compression version.

    I have purchased both the twin spark plug (medium compression) head (without decomp) and the twin spark plug (medium compression) head with optional decomp port, as well as his modified OEM 80cc pistons with 'machined' exhaust port and transfer port piston ramps.

    Do a Google search for "Twin Spark Plug Cylinder Head for 80cc Happy Time Engine" and you'll see detailed photos of the CR Machine Manufacturing cylinder head installed on my bike.
  14. jaguar

    jaguar Well-Known Member

  15. Fabian

    Fabian Well-Known Member

    Yes, it is one of about 12 photos of the pistons and the cylinder head and my setup
  16. scott.d.lang

    scott.d.lang New Member

  17. jaguar

    jaguar Well-Known Member

    I finally settled on using a home-made head gasket cut out of gasket material. It can flex with the slight normal head warping to prevent leaks. But the two surfaces have to be planed flat beforehand using sandpaper and glass. Added benefit is that it somewhat insulates the cylinder from the head so that the engine parts are subject to less heat and therefore last longer.
  18. Waxxumus

    Waxxumus Member

    I havent had a leak in 550 miles.
    Wonder when my head gasket will blow.