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146cc dohc build

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#202 ·
Right on Chad. Remember the camshaft considerations I sent you. I know I put in there that the biggest mistake people make is putting to big of cams in. :p I didn't figure the longer intake would help on yours. You are already touching peak length. All that showed is you can go too long but it doesn't say that long is bad. Interesting on the carb huh. ;-)



For everyone else's benefit here are some excerpts from the considerations...



The most common mistake with choosing a cam is to much duration.



If the head you are using has good low lift flow then the engine won't require as much duration. At the same time, if the ports are large and lazy use less duration and overlap to increase cylinder pressure and volumetric efficiency.



Match valve lift to port flow and valve head diameter.



...Also use less overlap when low lift flow is high and ports are not lazy.



:D
 
Discussion starter · #204 ·
yeah jordan thats what was going threw my head when i first thought about it. so does that mean i have big lazy ports??? very interesting on the carb i must say i kinda doubted your choice of carbs but i did it any how cause you haven't steered me wrong yet and just so happens your right that pe diffently out performed the pwk on my set up by at least 1/2 a horse threw out the whole power band. what do you think if i shortened my intake by a inch?
 
#206 ·
Chad you definitely don't have lazy ports. They could probably stand to be slightly larger on the short side radius but I'd hate for you to go to far. To much is worse than not enough. Shoot me the cam info again for the cams you have in now and I'll give you a yes or no as far as going shorter on the intake. I can tell you now an inch is probably too much. 1/2 inch might be a possibility but let me know on cams before I say yes or no.
 
#207 ·
awesome thread and awesome build. this is why i keep coming back to planet minis. to see people pushing it and doing things the hard way. just out of curiosity, what kind of $$$ are you looking at after the build was said and done?
 
Discussion starter · #209 ·
lol i am fortunate to have great people around me so i get killer deals i am not going to say specific prices cause i don't wanna get any one in trouble but i have less in this motor than what you can buy a stage 3 dohc from two brothers. :) but that falls back to getting killer deals my dad does the machine shop thing so i have access to the machines so i don't have to pay the huge bill to have someone do it for me. cycle pm sent
 
Discussion starter · #210 ·
got a good question for everyone. how much does an oil cooler work? i found that with this big cc i get to run it about 1/2 hour then it gets so damn hot the oil starts to break down and it smokes like a train. and what do you all need to hook up to a dohc?
 
#215 ·
haha ya u better get an oil cooler chad im tired of having to wait and hour when were riding so that danm thing can cool down but idk if thats a good idea as much as u wreck u are probly going to break it j/k -still kick ur ass on the track though-
 
Discussion starter · #216 ·
yeah dom you read right i dont have an oil cooler on my bike i have read numerous places that they are over rated. and seeing how i never had a heating problem before i didn't feel the need to use one i felt they were just a realiablity cause you tangle with people so many times on these lil things i figured it would be just my luck i'd rip a line and bam there goes my motor.



burn how about you shut up your a lil bitch you won't climb that hill or race with us on the track
 
#217 ·
When you cross the line from ride around pit bike... to strictly race engine... then the engine only has to serve it's purpose long enough to last a moto at a time. If you are heating up that bad... an oil cooler will buy you an extra two minutes.
 
#218 ·
maybe dual oil coolers...dont know how well it works or how much better it actually is, but it looks trick.
 
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Discussion starter · #219 ·
see thats what i thought would be the case with an oil cooler thats why i never bought one. also disscussed duals with micro75 but like i said wasn't so sure if they worked or not. oh well it was worth asking. looks like i'll just have to build me a china motor to play on
 
#220 ·
Two oil coolers overcooled my 143cc when the weather was 70-75 degrees. Now, I only have one cooler on it and it runs hotter than I like at 80-95+degrees. Hard to imagine that that little change in ambient temp causes the engine temps to go up so high.



Run an oil cooler on this engine...it will definitely help. Run it off the clutch cover though so you don't starve the head. Alternatively, you can take the oil out of the clutch cover and return it to the head with the cooler between...that would give you the most bang for your buck and keep the expensive parts lubed with cooler oil.
 
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