what mods wil make your engine go higher rpm's

[Huffydavidson]

NOW this is more realistic . let's go volcano sleding but put together a group.
will call it the Donner Party . I'd LMAO but I've got lava up my a$$.

 

[maniac57]

We're ready!

 

[mapbike]

NOW this is more realistic . let's go volcano sleding but put together a group.
will call it the Donner Party . I'd LMAO but I've got lava up my a$$.

Dont really think laughing it off would be a problem because a sled ride down the lava would likely scrape it off.......

wow.. what in the heck does any of this have to do with "what mods wil make your engine go higher rpm's"....?

Hey, maybe its just me thats missed the connection.......LOL!

Map

 

[Scott.D.Lang]

Im up for the sled ride as long as I can strap a rocket and parachute on it first

 

[Huffydavidson]

Get yourself a killer expansion chamber stay away from the toys like that JOKE
OF A PIPE Voodoo fea-bay trash . magic spells and potions don't work on motors.
LMAO

 

[mapbike]

Get yourself a killer expansion chamber stay away from the toys like that JOKE
OF A PIPE Voodoo fea-bay trash . magic spells and potions don't work on motors.
LMAO

Amen brother HuffyD!

A good flowing pipe, a well tuned carb and well ported jug are all recipes for more RPMs.

Using a better balanced lower will make those rpms increase and much more comfortable also.

Map

 

[rogergendron1]

honestly why do you care how many rpms your engine can handle ???

i dont care one bit lol

the only thing i care about is how much power i can produce at the rpm's my motor will run without exsesive wear.

so for me a race motor would turn 8,000 max but be ported timed and tunned to produce the most power possable between 4,500 and 8,000 rpm.

then gear it to go the speed you wish to achieve at a given rpm ... get it

so i build it to produce all my power around 6,000 to 8,000 then i gear it to go 35 - 45 in those rpms, this leaves me with enough torque to still climb hills and take off and pull out of coners, a smaller gear would take torque away and make it take longer to reach the top speed but top speed would increase.

a bike built like this will usualy always win against a bike that is just built for super high rpm's because those bike will not build power untill they are in those super high rpm's and by the time they get up in the rpm range i am already blown past them lol however high rpm small sprocket short power band bikes do have there place in wide open long track racing.... they are compleatly useless on the street though . forget about climbing a hill and every take off from a dead stop will be heck on your clutch ! you will have only 2 speeds WOT and stop lol

 

[mapbike]

My Gen IV dax lower build will spin over 9000rpms and has the power to slip the clutch a little sometimes which is very tight adjusted in the lower to mid rpms, good compression, well tuned carb, good port work, and the right exhaust can have an engine pulling hard up at the 9000+rpm range and still have good power in the lower to mid range area also, its all about having it set up right and then you can gear according to how you plan to ride, some of the lower to mid pull will be determined by the weight of the rider as well since these are such small cc engines.

In my experience, even when everything else is good for high rpm flow on the little engines exhaust flow will make or break what they will ultimately be able to achieve, a restrictive exhaust will kill the rpm potential on these little engines in my experience, as a matter of fact I'm dealing with that issue right now on two of my bikes, I changed the exhaust and lost upper rpms which has resulted in top speed loss as well, gonna be sorting this out as I can and getting it corrected asap..... I like my 40+mph cruise speeds!

Map

 

[48ccbiker]

Getting it to rev up to 11K is possible but you will lose power at lower rpm. Do you really want to be pedalling till it gets to 15 mph each time?
But if you really want to do it then;
drill the crank balance holes with a high strength 12mm drill bit.
use a 18mm or larger carb with the intake manifold bored out to match.
if you want a reed valve only the Arrow reed allows enough flow.
put on an expansion chamber and experiment with different header lengths till it allows the right top rpm. (shorter=faster)
increase the engine compression by lathing off 1.5mm from the head.
raise the exhaust port, starting with 2mm and then keep raising it little by little till you acheive the top rpm you want.
lower the intake port 2mm.
raise the transfer ports 1mm.
put on a hi-RPM Jaguar CDI (announced on the other forum).
actually it is best to put on an expansion chamber and tune it as the last step since you can go as fast as you want with a stock pipe. the chamber will give better hi rpm power but its length determines how high the engine can rev.

 

[Huffydavidson]

A high rpm jag now that's FUNNY CHIT . I build the lightening and it is far superior to the Jaguar. The jag and its pee wee 3.3uf timing cap, why that just laughable with the timing curve starting at 6800rpms hahahaha dudes got jokes.

 

[Dogtown Burner]

Getting it to rev up to 11K is possible but you will lose power at lower rpm. Do you really want to be pedalling till it gets to 15 mph each time?
But if you really want to do it then;
drill the crank balance holes with a high strength 12mm drill bit.
use a 18mm or larger carb with the intake manifold bored out to match.
if you want a reed valve only the Arrow reed allows enough flow.
put on an expansion chamber and experiment with different header lengths till it allows the right top rpm. (shorter=faster)
increase the engine compression by lathing off 1.5mm from the head.
raise the exhaust port, starting with 2mm and then keep raising it little by little till you acheive the top rpm you want.
lower the intake port 2mm.
raise the transfer ports 1mm.
put on a hi-RPM Jaguar CDI (announced on the other forum).
actually it is best to put on an expansion chamber and tune it as the last step since you can go as fast as you want with a stock pipe. the chamber will give better hi rpm power but its length determines how high the engine can rev.

Hey Fellas,
Listen to this guy! This is how you make a race engine.

There are of course more specific aspects of the port timing adjustments ( use a degree wheel rather than just 'hacking away a mm here, mm there") But if you just do these things you'll have a totally different engine. Also grab a high compression head!. we carry the best ones available, but there are many places to get one.

 

[Scott.D.Lang]

Hey Fellas,
Listen to this guy! This is how you make a race engine.

There are of course more specific aspects of the port timing adjustments ( use a degree wheel rather than just 'hacking away a mm here, mm there") But if you just do these things you'll have a totally different engine. Also grab a high compression head!. we carry the best ones available, but there are many places to get one.

I almost agree 100% except for the jaguar I say use a HD from fred

 

[rogergendron1]

mm yup port it wide open and get a puch 70 hihhi, then a larger carb 16mm or better the delorto phgb or mikuni vm18 will do and a short billit port matched intake manifold and a custom made exhaust for your riding style.

the reed valve kits will help you with throtttle responce and fuel mixing but its not needed in my experiance . i own a 40 pluss mph bike and its jut a standard piston port.

 

[SuperDave]

You wanna build a 11,000 RPM screamer? Go ahead, I'd love to drag race you for a block or two if & when you get it running. I'll be at the finish line before you get your motor wound up to 4000 RPM. That kind of motor won't make any usable power that would even resemble streetable manners.
You'll have to pedal 15-20 MPH before it'll even start, idle at 2,000 RPMs, and unless it's been balanced, most every nut & bolt will rattle & fall off of your bike before you burn through a single tank of fuel.

I recommend what Rogergendron1 suggests, build for dependable power, then gear it for speed.

11,000 from a China Girl, LOL! Hope you got your insurance premiums paid up, if you ride that thing at those speeds for long, you're gonna find yourself under a surgeon's knife extracting shards of your 11,000 RPM engine out of your buttocks, rectum & scrotum! But seriously, if you really want to go that fast on 2 wheels, buy a motorcycle.

 

[Gp masta]

Getting it to rev up to 11K is possible but you will lose power at lower rpm. Do you really want to be pedalling till it gets to 15 mph each time?
But if you really want to do it then;
drill the crank balance holes with a high strength 12mm drill bit.
use a 18mm or larger carb with the intake manifold bored out to match.
if you want a reed valve only the Arrow reed allows enough flow.
put on an expansion chamber and experiment with different header lengths till it allows the right top rpm. (shorter=faster)
increase the engine compression by lathing off 1.5mm from the head.
raise the exhaust port, starting with 2mm and then keep raising it little by little till you acheive the top rpm you want.
lower the intake port 2mm.
raise the transfer ports 1mm.
put on a hi-RPM Jaguar CDI (announced on the other forum).
actually it is best to put on an expansion chamber and tune it as the last step since you can go as fast as you want with a stock pipe. the chamber will give better hi rpm power but its length determines how high the engine can rev.

Great tips...

 

[mech_engineer]

Notch the piston on exhaust side the deeper the notch more rpm try .5mm at a time test and increase again other .5mm

 

[mech_engineer]

This will narrow you power band more hp at high rpm notch the piston skirt on intake side 1mm

 

[mech_engineer]

 

[mapbike]

I'd be leery of grinding that deep down I to the ring groove, I ramp my pistons on exhaust and at thr transfer ports but I dont remove near that much material, when Im finished with mine half of the material between upper ring groove and top of piston edge is still there, seems you're putting a lot of hot gas behind that top ring with that much material removed.

Not saying it wont work but im not sure thats a good idea to have that compression ring xposed fully to combustion in that area.

Map

 

[2door]

I just read through this thread and wondered if any of you have noticed that after 38 posts, the OP only posted twice?

Lots of good and lots of very bad advice given. But probably wasted.

Sorry, just an observation.

Tom