3 hp 127 cc performance help?

Drew Fields

New member
I have a 3 hp flathead that is stock model 80212 and was wondering if there are any compatible performance parts available that I can install or any recommended mods I can do to get hp gains ? This engine is going on a mini bike
 
I'm not going to say there arent any performance parts for the 3hp flathead,but i have never been able to find any for the two 3hp engines i have.. But you can go with exhaust springs on both int. & exh. a lil carb work, and bump the timing up a hair will pick it up some...
 
When we used to build the mini-Indy celebrity, Shriner, and jr 1/4 midget race engines using the 3HP flatheads, we would concentrate on carb and valves/seats. You can install hi-flow valves - that'll help somewhat as well. Then we'd twist the cam and cut the deck and head to increase compression slightly. I don't recall if Dyno ground a cam for us -- (IF they did, it was the same profile as the 89-7exp - but man, it's been at least 20 years since we did these engines.)


-----
?Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
www.CarlsonMotorsports.com
Carlson Motorsports on Facebook
30 years of service to the karting industry
Linden, IN
765-339-4407
bcarlson@CarlsonMotorsports.com
 

Mac_49

Premium User
Unless it's for sizing issues, you honestly might be able to get a nice 5hp flatty on here for the same price you'll be spending to get any gains out of the little 3hp. Just something to think about.
 
^ Agreed.
I second that but as of right now this lil 3 hp I have is pretty peppy. I have just cleaned and smoothed out the kinks and rough edges externally so far and it is a night and day difference on the ol mini bike. I do have a problem starting this morning tho. I cut down an old Dover pipe and got a two stage straight pipe from it. I threaded it on the inside then used a pipe coupler to connect it to the exhaust port since there is only a thread option for installation. I also added a RLV B-91 silencer. So far is good and bad. Tons of bottom end torque compared to b4 and a wide range of tuning on the screw but it has to be just right to get the most out of the top end power and it is idling way to high even with the idle screw all the way backed off. Does this mean I need to re-jet? if so what way and if not whats the magic word plz? Thank in advance sorry so long.
 
I second that but as of right now this lil 3 hp I have is pretty peppy. I have just cleaned and smoothed out the kinks and rough edges externally so far and it is a night and day difference on the ol mini bike. I do have a problem starting this morning tho. I cut down an old Dover pipe and got a two stage straight pipe from it. I threaded it on the inside then used a pipe coupler to connect it to the exhaust port since there is only a thread option for installation. I also added a RLV B-91 silencer. So far is good and bad. Tons of bottom end torque compared to b4 and a wide range of tuning on the screw but it has to be just right to get the most out of the top end power and it is idling way to high even with the idle screw all the way backed off. Does this mean I need to re-jet? if so what way and if not whats the magic word plz? Thank in advance sorry so long.

It's possible that you have an air leak too.
If the exhaust is too restrictive, it could be preventing it from running correctly at higher rpm.
You can certainly play with the jetting, but I'm guessing that's not the problem. Stock jetting should be fine with a stock bore carb. If you've made the bore larger, then of course you'll have to increase the jet size proportionally.
Then again, if you made the bore/venturi larger where the butterfly sets, you would likely need a larger butterfly to close the air down to get it to idle correctly.
 
It's possible that you have an air leak too.
If the exhaust is too restrictive, it could be preventing it from running correctly at higher rpm.
You can certainly play with the jetting, but I'm guessing that's not the problem. Stock jetting should be fine with a stock bore carb. If you've made the bore larger, then of course you'll have to increase the jet size proportionally.
Then again, if you made the bore/venturi larger where the butterfly sets, you would likely need a larger butterfly to close the air down to get it to idle correctly.
Air leak for sure.
 
When we used to build the mini-Indy celebrity, Shriner, and jr 1/4 midget race engines using the 3HP flatheads, we would concentrate on carb and valves/seats. You can install hi-flow valves - that'll help somewhat as well. Then we'd twist the cam and cut the deck and head to increase compression slightly. I don't recall if Dyno ground a cam for us -- (IF they did, it was the same profile as the 89-7exp - but man, it's been at least 20 years since we did these engines.)


-----
?Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
www.CarlsonMotorsports.com
Carlson Motorsports on Facebook
30 years of service to the karting industry
Linden, IN
765-339-4407
bcarlson@CarlsonMotorsports.com
Brian how far is Linden from Elwood?
 
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