Timing vs performance

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Lecheroandpuertorro

Lecheroandpuertorro

New Member
May 1, 2011
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Puerto Rico
Hi friends one warm regard from Puerto Rico
i read some threads in this forum in reference of the ports in the cylinder and some mods to give performance.But some days ago i talk with a old school friend and said me its work in a repair shop,he said me in the shop modify the engine of a bicycle with amazing results.i read with some cutoff in the intake and exhaust the difference is great but is the first time i listen this, they cutoff a 2 mm in the up side in the intake of the cylinder and cut off a 2mm in the bottom side in the exhaust.
What is the idea of this port?Only one change the timing of the cylinder he said that is the best timing for top speed obviously with other carb,head,sprocket mods.The results is amazing 60mph with one gear no shift kit in my case i dont believe that i have a speed gun i need see this speed with my eyes i wanted this bike to confirm that please take me some days
Now the question someone is tried this port in the forum?really is the best to top end?.shft.
i apreciate you opinion
 
rustycase

rustycase

Gutter Rider
May 26, 2011
2,746
5
0
Left coast
Port timing, raised compression, tuned pipe, improved carby, and balancing will all make an improvement to these little ht china girls.

bbbut they will never be a morini.

Achieving what is calc'd out to 12k rpm is beyond what I'd be inclined to believe, also.

But 'goals are important...'
"I learned that in rehab." :)
rc
 
BarelyAWake

BarelyAWake

New Member
Jul 21, 2009
7,194
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Maine
First off, I'd like to mention the OP wasn't referring to his own motor, mentioned he didn't believe it himself, never said what type/make/model of engine other than "the engine of a bicycle" and in fact hasn't made another post at all in over two months.

Then there's these small points of interest..

Units of measurement are mixed in Puerto Rico, for example distances are indicated in kilometers whereas speed limits are in miles per hour... & 37.28mph = 60kph

Which infers a far more likely possibility than 60mph.
 
Last edited:
decoherence

decoherence

New Member
Aug 23, 2010
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sebring,fl
1974paris said:
36.0 mph thats my new record am waiting for some more spark and timing to fix my top end 4stroking.xct2
Click to expand...
that isn't going to help as much as making it not run as rich.
also the timing will affect the whole rpm range unless you get a circut that retards @ higher rpm.
 
Lecheroandpuertorro

Lecheroandpuertorro

New Member
May 1, 2011
27
0
0
Puerto Rico
BarelyAWake said:
First off, I'd like to mention the OP wasn't referring to his own motor, mentioned he didn't believe it himself, never said what type/make/model of engine other than "the engine of a bicycle" and in fact hasn't made another post at all in over two months.

Then there's these small points of interest..

Units of measurement are mixed in Puerto Rico, for example distances are indicated in kilometers whereas speed limits are in miles per hour... & 37.28mph = 60kph

Which infers a far more likely possibility than 60mph.
Click to expand...
Hi barely and friends
in first time you are the reason not its my bike but its a local bike with a china engine I went to see the bike but could not they tell me the owner was imprisoned say is true but I want to see bike I've seen here in Puerto Rico running 52 mph. Mine personally has come over me that 46.5 mph Weight 250 lbs and it was straight down a slope.Barely not mention the mileage now that I make something clear Puerto Rico is part of U.S. and the measure of speed is the same that you use there, very clear in my letter says mph I felt as if you wanted that here we do not know the difference between mph-,-kph.Sorry for not writing it to 60 mph bike before but do not use the pc all days thanks for your comment but barely read well you know a lot of this more than I that's for sure
 
BarelyAWake

BarelyAWake

New Member
Jul 21, 2009
7,194
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0
Maine
Usually a sign of an excessively rich fuel/air mixture in a two stroke under load, it sputters a bit, feeling like it's missing every other stroke. A piston ported, unreeded two stroke "four stroking" when not under full load is normal however, showing that the fuel/air mix is just about optimum.
 
M

Mozenrath

New Member
Jan 13, 2011
340
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California
From what I've read, it's not impossible to make our engines go 60+ mph, but it's largely impractical. To go 60, from what I think I know, you'd need at least a 22 tooth sprocket and you'd have to be riding straight on a completely flat grade. I don't think you could do such a thing in traffic or with any hills. For normal use in traffic, it's not possible, but for the purpose of just trying to go fast on a straight track, it doesn't seem impossible.

I don't know much about altering engine timing, but it seems very farfetched that just changing the timing would double performance. I suggest OP takes an actual speedo or GPS speed to confirm. I remember when I was first riding my MB, I thought I was going 40 mph, but it's easy to think that since you're much closer to the road than you are in a car. My bike right now gets a maximum of 32 mph on a flat road.
 
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