New Slant Heads for 80cc's: Compression Boost!?

I got my new slant head but am having trouble mounting it. With the extra gaskets, the amount of bolt protruding though the head is barely enough to screw on the acorn nuts. I used 3 of the thin paper gaskets at the bottom and 1 metal on the head to keep the piston from hitting it. But the combination of the 4 gaskets and the possibly thicker head, the 8m bolts that come though the head are now really too short to properly tighten down the acorn nuts. I removed a washer from each bolt leaving only a lock washer and the nut but I am barley able to get enough revolutions on the nut to consider them secure. Was this an issue for any one else? I tried my local Ace hardware store but they didn’t have that size all thread. Any suggestions? They are the 8m-1.0.
I did tighten then enough for a brief test run. Its running pretty bad but I haven’t tried adjusting the carburetor yet. I did take the opportunity to port the intake and exhaust while the bike was out of commission. I did as little as possible and only removed sharp edges from the casting. I did remove quite a bit of material on the pipe from the carb to the intake to try and enlarge it to match up better. I am planning on buying SBP expansion chamber pipe when they are back in stock. Should I wait till I install the pipe to try and tune it or will making it run better now make it easier to adjust with the new pipe?
 
At some point (such as 4 gaskets!) I fail to see any advantage. Sounds like your engine just won't benefit much....I mean the main gain is compression (and squish zone) - NOT the shape of the head......I'm just saying, maybe all sorts of tuning might get it running half way decent, but in the end have you gained anything? I'm just saying, I'm not saying.....

Yeah, you won't find M8x1.0 at Ace or most retail places.
 
Sick Bike Parts has them as a set. They are a little short though, they need to be another 1/2" longer at least ( to double nut ).
 
Ok, well I got some that were cut short by mistake then. After seating the studs fully
I couldn't get the nuts with the washer and lockwasher all the way threaded on.
I had to have the head bosses taken down for that. I need to use the thicker head gasket for the
slant head that I bought. I'll get it to work, I just figured to use a double nut arrangement
and another 3/8 to 1/2" would do it with no shortening to the bosses.
 
Are you saying there was not enough room for a single nut? They are not designed for double nuts.
 
Yeah, they were short 1 or 2 threads and did not go flush to the top of the nut. That was with the thin head gasket. I'll get it sorted out, just thought I'd let you know for future reference. It would be nice to be able to add a locking nut though.
 
Interesting, thanks. I actually made them a few mm longer than stock (and I thought people would complain about them being too long :o ). I wonder if you have super deep holes in your block(?) - which is a good thing.
 
Let me say that you guys have a good thing going there. Except those exhaust systems
selling too fast for me to get another one ... ;)
 
Update on my slant head bolt length problem.
I went with 3 thin paper gaskets because I thought I heard the piston hitting with less. I bought a set of higher quality bolts from SBP mainly because the acorn nuts had started the rust from a late winter ride on wet still salty streets. I decided to start from scratch. I went back to step one and tried again with one paper gasket on the bottom and the metal one on the top. I took the suggestion that someone had made about pulling the plug and rolling the bike. No piston slap. I guess if you are looking hard enough for something you will find it, even if it’s not there.
Yes, there is a very noticeable difference in the amount of pull from a stop. Buy it.

“Isn’t fun the best thing to have?" Arthur (Dudley Moore)
 
I just installed a slant plug engine from BOYGOFAST 68.5cc, it is much more powerful than my 65.9cc stinger JET SILVER
 
Pablo said:
Interesting, thanks. I actually made them a few mm longer than stock (and I thought people would complain about them being too long :o ). I wonder if you have super deep holes in your block(?) - which is a good thing.
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If you thread studs all the way on a stock engine there will not be enough room to fully thread nuts on top. Stock studs are too short. They are normally screwed in only part way.

I don't see how it's possible to make them too long. Even an inch longer couldn't hurt. If the extra length bothers you they can be cut down. Easier than trying to stretch them out. :)
 
xlite said:
If you thread studs all the way on a stock engine there will not be enough room to fully thread nuts on top. Stock studs are too short. They are normally screwed in only part way.

I don't see how it's possible to make them too long. Even an inch longer couldn't hurt. If the extra length bothers you they can be cut down. Easier than trying to stretch them out. :)
Click to expand...

You have a point - I just figured people would complain about flag poles sticking up in the brreze!
 
Pablo said:
You have a point - I just figured people would complain about flag poles sticking up in the brreze!
Click to expand...

Now that I think of it the acorn nuts might be a bit of an issue in that case too!

In fact they're the only stock hardware I actually replace if I'm unlucky enough to get an engine with those on it. Ever since popping the the tops off a set many years ago.
 
I don't think many here that play with the engine much or order head studs use the acorn nuts.
You just can't get a proper torque without risking stripping the thread in the case. Am I wrong ?
 
No your right, I personally use nylocks on my head. With brass flats and bronze lock washers. The head doesn't seem to get hot enough to affect the nylocks and I just like the color of the brass washers. I've tried the slanthead both directions. Plug forward and back it made no difference at all in the way the motor ran.
 
I've got both motors, the slant motor runs way better than the straight plug, my bike hits 40mph easily and i'm not light.
 
HotWheels, are you using the thick or thin gasket ?? is there about an 1/8th inch from the
piston edge to the top of the cylinder ? These motors seem to have a lot of differences
between the makers.
 
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