Slant cylinder head vs. strait cylinder head

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bulljo

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Jan 5, 2013
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Never tried the 50cc but i have tried the 70cc the 50cc might be too much compression for a little 66cc that could lol ur gonna wanna buy a few leaner jet sizes too and lap the head to make sure you get a good seal!
 
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Frogster

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Jan 18, 2013
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I actually have the 50 cc puch hi hi head, and I am going to put it on after the motor breaks in. Having carefully inspected my piston and spark plug clearance, I honestly think it will work properly. It will just create alot of compression! We will see how it goes, however as far as clearance issues go, there are none for my66 cc engine
 
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bulljo

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Say frogster did you upgrade your bearings because mine blew out after a hundred miles after changing to this head on two different motors. And but i forgot to mention that adding compression might not be as beneficial as say adding compression after porting the head, intake,exhaust,piston and crankcase transfers.
 
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Frogster

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Jan 18, 2013
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Well bulljo I have not got the bike running yet due to time constraints, however I bought a flying horse branded motor which claims to have high quality japanese bearing. If they do fail, I have a friend whos dad owns a bearing distribution company so that should help me out. I am not going to put on the puch head until I have broken in the motor. Also, I cleaned out the crankcase with a couple of wd-40 baths and was appalled at how much metal dust I actually cleaned out of the brand new crankcase. I posted a thread about it about a week ago somewhere on this website if you want to see a picture. I have indeed ported out my cylinder jugs exhaust intake and transfer ports being carefull to follow the advice about porting found on this website. I also matched the gaskets. I hope that after a good break in period with the stock head, I can bolt on the puch 50cc hi hi head, and run 94 octane gasoline with a high performance synthetic 2 storke oil. Im thinking ill get some royal purple. Hopefully the high octane gas and high quality synthetic oil will do the trick to make this puppy pick up like a mofo on the low end and not destroy itself.
 
KCvale

KCvale

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Feb 28, 2010
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Frogster said:
I hope that after a good break in period with the stock head, I can bolt on the puch 50cc hi hi head, and run 94 octane gasoline with a high performance synthetic 2 storke oil.
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That sounds like a good plan but don't confuse higher octane with more power, octane is an ignition suppressant to keep a high compression gas/air mix from per-igniting, aka Knock.

You won't have that problem but I run premium in all motorized bicycles anyway because it is usually 'cleaner', meaning less ethanol, BTMB, whatever crap they put in the cheap stuff and at 100MPG I can splurge ;-}
 
BarelyAWake

BarelyAWake

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Jul 21, 2009
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KCvale said:
That sounds like a good plan but don't confuse higher octane with more power, octane is an ignition suppressant to keep a high compression gas/air mix from per-igniting, aka Knock.

You won't have that problem but I run premium in all motorized bicycles anyway because it is usually 'cleaner', meaning less ethanol, BTMB, whatever crap they put in the cheap stuff and at 100MPG I can splurge ;-}
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Consider for a moment that "premium" is no more refined or filtered than the others, that ethanol is used to raise octane levels & "premium" means the highest octane available, that ethanol blend fuels have a shelf life of 30-90 days from the refinery before it undergoes phase separation and water contamination, that due to high prices the "premium" fuel doesn't sell nearly as well as the less expensive options so it sets there the longest, that ethanol itself is a solvent, that the stations don't pump out the remaining fuel before refilling the ground tank...

...are you sure that "premium" has less "crap" in it?

I would suspect it depends entirely on the particular station, what they sell the most of (the "freshest" fuel") and their pump, hose & tank maintenance habits. Does your local station sell enough "premium" to cycle their tanks completely every 30-90 days?

Mine sure doesn't ;)
 
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Frogster

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Jan 18, 2013
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Lol guys relax. I understand the concepts of octane use in compression applications dont worry. The reason I plan on using high octane Is I want to avoid engine knock. Keep in mind I am using a high compression head intended for a moped cylinder bored out to 50 cc on a 66cc china engine. there is a flat area of around 5mm around the edges seperated from the piston only by the head gasket, before the combustion chamber opens up. I am literally pushing the compression level to the limit on this engine.. I need the higher octane to avoid having premature detonation. I have triple filtered my fuel line before it gets to the carb and Ive gotten an ada racing high flow air filter aswell. I have a focus on making sure everything going into the engine is filtered as best as possible. I am going to buy a bottle of royal purple high performance 2 cycle motor oil after the engine is broken in. This will deal with properly lubricating my engine even under the heavy demands put on all the bearings by the very high compression and the expansion chamber exhaust I will put on it.
 
Scott.D.Lang

Scott.D.Lang

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Jan 1, 2013
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I just read the entire post and all this started with is a slant plug head are better then a strait head. That said I personalty dont see how because of my experience with 4 stroke engines a strait plug head is always better as long as the plug is in the center of the cylinder. Most Imports are running a HEMI style head on there engines and there are a couple reasons for it first and maybe most important is the burn in the cylinder is much more even witch makes the whole process more efficient. So all that said I dont see how the slant head could be better except maybe they are higher compression but I dont know it all so I could be bad wrong on my thinking.
 
KCvale

KCvale

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Feb 28, 2010
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Slant heads are great when bike cavity room is an issue, I think they 'look cooler' when faced forward and CDI is on the front tube as well ;-}

You are going ultra performance so sure every bit helps, I look forward to seeing how that turns out.

As for fuel in my area here in Phoenix my local station has 36 pumps for demand and every state has different mixes of summer and winter blends.
I don't 'feel' any difference from one fuel to another like for example just using an Iridium plug makes, but call it psychological if you like, I just like filling up my 1 gallon can by going in the store and saying 'give me exactly 1 gallon of premium on pump 24' with people in line behind me ;-}
 
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bulljo

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orange county
Kcvale i would rethink using royal purple as they do not really test and meet all regulations but i recommend castor 927 and golden spectrum smells so sweet.
 
KCvale

KCvale

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Feb 28, 2010
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Phoenix,AZ
bulljo said:
Kcvale i would rethink using royal purple as they do not really test and meet all regulations but i recommend castor 927 and golden spectrum smells so sweet.
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The topic author talked about royal purple, I usually just use autozone 2-stroke oil but I did like Amsoil 100:1 synthetic, I mixed it at 50:1 to be safe and did notice a very slight increase in power on just a stock motor.
 
moonerdizzle

moonerdizzle

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Jun 28, 2009
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Cheese head capitol
BarelyAWake said:
Consider for a moment that "premium" is no more refined or filtered than the others, that ethanol is used to raise octane levels & "premium" means the highest octane available, that ethanol blend fuels have a shelf life of 30-90 days from the refinery before it undergoes phase separation and water contamination, that due to high prices the "premium" fuel doesn't sell nearly as well as the less expensive options so it sets there the longest, that ethanol itself is a solvent, that the stations don't pump out the remaining fuel before refilling the ground tank...

...are you sure that "premium" has less "crap" in it?

I would suspect it depends entirely on the particular station, what they sell the most of (the "freshest" fuel") and their pump, hose & tank maintenance habits. Does your local station sell enough "premium" to cycle their tanks completely every 30-90 days?

Mine sure doesn't ;)
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premium here is ethanol free from every gas station except for kwik trip.
 
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noco

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Sep 9, 2009
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fort collins colorado
Wow...all this from slant vs straight...lol...I was interested in this thread for the idea of raising compression, jetting much bigger say 10 to 1, instead of 14.7 to 1, then running e85. You can get more power from e85 than gas cause of the cooling properties of ethanol. Note that power is at full throttle. I did this to a cheap car of mine recently and it runs great. The only thing I'm trying to figure out now is how to advance the timing on the bike engine...I've experimented a few years ago with the 2stroke oil (cheap stuff from gas station) and it did not separate in e85. All this worry about minor percentages of ethanol in the fuel is just rumor...the fact is that gas is tougher on parts than ethanol...

I guess I my mind wondered . Huh...it seems to me that high compression could be done by planing factory heads and heat would not be an issue with ethanol instead of gas. I have an a 5yr old used flying horse 66cc sitting on a shelf(straight plug..lol). I should prolly see if I can take .030 off the head and try this.
 
dodge dude94

dodge dude94

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Jun 8, 2012
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noco said:
Wow...all this from slant vs straight...lol...I was interested in this thread for the idea of raising compression, jetting much bigger say 10 to 1, instead of 14.7 to 1, then running e85. You can get more power from e85 than gas cause of the cooling properties of ethanol. Note that power is at full throttle. I did this to a cheap car of mine recently and it runs great. The only thing I'm trying to figure out now is how to advance the timing on the bike engine...I've experimented a few years ago with the 2stroke oil (cheap stuff from gas station) and it did not separate in e85. All this worry about minor percentages of ethanol in the fuel is just rumor...the fact is that gas is tougher on parts than ethanol...

I guess I my mind wondered . Huh...it seems to me that high compression could be done by planing factory heads and heat would not be an issue with ethanol instead of gas. I have an a 5yr old used flying horse 66cc sitting on a shelf(straight plug..lol). I should prolly see if I can take .030 off the head and try this.
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I have a feeling you're going to find that the engine is just going to run hotter and that your actual power increase will be from the compression bump.

The statement that ethanol has cooling properties is BS as alcohol requires more energy to burn, therefore generating more heat. The ethanol has a higher octane rating, thus, a lower BTU number, thus, less energy. And as far as ethanol hurting the engine, yes, yes actually it does. Now, 4 strokes are likely hurt more then 2 strokes as the 4 strokes are ingesting TWO straight solvents and 2 strokes, just one as the oil adds lubricity to the fuel. And of course E85 won't separate, ****, I haven't ever caught my 2 stroke oil separating in my E10 after a year. It's not supposed to. The E85 also won't separate as much because there is more alcohol to participate in phase separation, so it doesn't have far to move.

I have a feeling that, unless you advance your timing 30*, you won't see any power increase from E85 and just get a heat increase. But, hey, experiment with it.

Either way, I hate that shiznit.
 
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noco

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Sep 9, 2009
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From experience I converted a 2.3l Volvo to e85 because it failed emissions for nox which is caused by too high of combustion temps...I did have to find some junk yard injectors that flowed 1.42 percent more fuel. This thing came with a knock sensor and advanced its timing itself. I planed the head and have 180ish psi compression. It really works well. I did bring my fuel mileage down from 28 to 24 though... And ethanol isn't bad for the motor like methanol which I find most people are abit confused on...I'm sure about that cooling effect. And ethanol burns cooler than gas...I'm just staring at that old flying horse right now trying to figure out how I can increase my spark timing...if you think of anything man let me know
 
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Wild Bill

Wild Bill

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Jan 29, 2013
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Camarillo So. Cal.
noco said:
Wow...all this from slant vs straight...lol...I was interested in this thread for the idea of raising compression, jetting much bigger say 10 to 1, instead of 14.7 to 1, then running e85. You can get more power from e85 than gas cause of the cooling properties of ethanol. Note that power is at full throttle. I did this to a cheap car of mine recently and it runs great. The only thing I'm trying to figure out now is how to advance the timing on the bike engine...I've experimented a few years ago with the 2stroke oil (cheap stuff from gas station) and it did not separate in e85. All this worry about minor percentages of ethanol in the fuel is just rumor...the fact is that gas is tougher on parts than ethanol...

I guess I my mind wondered . Huh...it seems to me that high compression could be done by planing factory heads and heat would not be an issue with ethanol instead of gas. I have an a 5yr old used flying horse 66cc sitting on a shelf(straight plug..lol). I should prolly see if I can take .030 off the head and try this.
Click to expand...

On a 2 stroke you actually dont want too much timing advance on the top end you want the opposite. I gained 2-3 mph by actually taking some timing advance out with a Jaguar ignition.
 
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noco

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Sep 9, 2009
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Why is that bill... Could you explain abit ... That just doesn't make sense to me...you know we all always have something to learn, that Volvo taught the **** out of me...I'm a master mechanic for 20some yrs and I never had to think that much about fuel trim before lol...I don't know everything about 2strokes either but I'm having fun with it

Edit. Wow I didn't think that was a swear...lol
 
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noco

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Sep 9, 2009
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fort collins colorado
Ok I found my answer timing needs to be retarded after 7000rpm due to faster burn caused by turbulence. In general it is lower than a 4stroke due to heat on the piston face. Well ethanol should help reduce that heat. Now ethanol engines you want you highest pressure at 10degrees Atdc instead of 15 to 20 degrees. Hmm... Maybe I'll try keeping the stock timing and figuring the timing issue out after...if your saying that retarding the timing at high rpm helped maybe the stock timing might just be right...

Happy riding...
 
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