HF 196cc Mild Mods and Questions

#1
I have a HF engine that is going to be installed in a old Speeco 3 wheeler. I will be using it on our property and hauling deer on homemade small trailer. Biggest thing is to be reliable and a bit more low end power. The current mods as follows:

Governor delete. (left stock springs to limit RPMs due to running Baja heat flywheel and stator)

High flow air filter and valve cover breather

Idle rejet (74 bit) and main jet (65 bit) jury still out.

Pulse pump


Future mods

Billet rod

header with OEM muffler or tractor stack muffler (I am limited to 91 decibels on public lands)

GX160 head with mild porting

Give your thoughts or advise,

Thanks, Dan
 
#2
Might try either a 22mm mikuni carb or at least replace the emulsion tube with the 140cc honda part. I would upgrade your flywheel, rod and springs for safety. Controlling RPM with valve float is dangerous. If your on a budget I would get some 18# springs, an aluminum PVL flywheel and ACR rod. A flat top piston might be a cheaper option that replacing the head. I would upgrade to high ratio rockers too so you increase your lift with out adding duration. Once you can safely rev the motor higher I would change sprocket so you have more torque.

So if your asking for a minimum list, PVL aluminum flywheel, ACR rod, 18LB springs, 140cc emulsion tube and lower gears. This will not add HP but will allow the motor to say together long term and allow for low gearing so you can increase the torque you are putting to the ground.

If your looking at making more power I would add to this a flat top piston and the rocker arms. I would not spend the money on a new head unless your looking at getting a head with larger valves and some porting done to it but at that cost you might ass well try to upgrade to a larger motor.

Take all this as advice, I have build a lot of fast cars in my life but am new to the gokart and mini bike seen.
 
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#4
Given your requirements, keep the engine stock. It's plenty of reliable power right out of the box, definitely enough to haul deer.

Otherwise, here is some light reading for you on the most discussed topic on this forum.
This ^^^^^^^^^^

Leave it stock with the governor intact if you are going to load the motor and haul a small trailer with it. If you are looking for lower end torque, gear it that way. It will be plenty reliable for your needs. Once you mod it, remove governor & change carbs, you are pushing your peak torque higher up the RPM range away from where you need it for climbing hills.
 
#5
This ^^^^^^^^^^

Leave it stock with the governor intact if you are going to load the motor and haul a small trailer with it. If you are looking for lower end torque, gear it that way. It will be plenty reliable for your needs. Once you mod it, remove governor & change carbs, you are pushing your peak torque higher up the RPM range away from where you need it for climbing hills.
SRY but this is not true. Removing the governor Dose not move the power band at all. It only allows the motor to spin more RPM. The power all the way up tell were it would have been cut off by the governor remains the same. The only way to increase power with the current motor are to change gear ratio, increase compression as far as fuel will allow, increase timing as far as fuel will allow, improve the VE, optimize the fuel ratio if possible, increase the CC of the motor with a larger bore and stroke.

I would mod the motor so it holds together at high RPM and put a very low gear in it.
 
#6
SRY but this is not true. Removing the governor Dose not move the power band at all. It only allows the motor to spin more RPM. The power all the way up tell were it would have been cut off by the governor remains the same. The only way to increase power with the current motor are to change gear ratio, increase compression as far as fuel will allow, increase timing as far as fuel will allow, improve the VE, optimize the fuel ratio if possible, increase the CC of the motor with a larger bore and stroke.

I would mod the motor so it holds together at high RPM and put a very low gear in it.
I agree with this, just going by tuning on my predator. I put a chikuni vm22 on it and indeed there was a loss of low end compared to the stock carb. But I did put a new cam that had a different LSA. So this pushed the peak torque higher up. You didn't mention above adding a new cam. I have basically done what you have said in building it for high rpm and low gear, black mamba sr cam geared 6:1. At first gearing was 5:1, a dog down low 6:1 is much improved, gearing was the main biggest bang mod. I do feel that putting a larger carb like the vm22 will indeed move the peak torque higher up, again just based on my experience. Correct me if I'm wrong. Still learning all I can :thumbsup:
 
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#7
Dave nailed it. Leave it stock. If anything, a Stage 1 with the governor in tact would be the Max needed. If geared correctly or a TAV is used, it will perform. very well.


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#8
I agree with this, just going by tuning on my predator. I put a chikuni vm22 on it and indeed there was a loss of low end compared to the stock carb. But I did put a new cam that had a different LSA. So this pushed the peak torque higher up. You didn't mention above adding a new cam. I have basically done what you have said in building it for high rpm and low gear, black mamba sr cam geared 6:1. At first gearing was 5:1, a dog down low 6:1 is much improved, gearing was the main biggest bang mod. I do feel that putting a larger carb like the vm22 will indeed move the peak torque higher up, again just based on my experience. Correct me if I'm wrong. Still learning all I can :thumbsup:
Ya I did not mention a cam because I don't know enough about these motors and there cams. Just looking at the specks it looks like almost all cams but maybe the CL1 high torque would sacrifice bottom end. I have never ran the CL1 so cant say how it would affect the very bottom end but know the rockers would make power every were. One thing that can add some bottom end torque on a larger cam is advancing the cam if that is a possible. You cant start making compression tell the intake valve closes and closing it sooner raises cylinder pressure, improves vacuum and lowers the power band. If at all possible getting the CL1 ground 4-6* advanced would further increase torque. One other reason I did not mention a cam is the cost of mods like this after all the other mods required like valve springs and the normal bolt on's is that it is almost better just to buy a larger motor like a 420 clone.
 
#9
Indeed leave the governor unless you plan on building it with billet parts. On my son's bike it has more than enough power to do anything you are describing and its bone stock. I suggest getting the trike going and try it before you start overthinking all the mods you "need". I'm guilty of it myself of overbuilding an engine for something.
 

SAS289

Well-Known Member
#10
I think this thread alone helped me decide on what mods I should plan on for my new Coleman's. Stay governed, get better breathing, rejet, and install a TAV. I have no need for speed. Thanks everyone!
 
#11
I think this thread alone helped me decide on what mods I should plan on for my new Coleman's. Stay governed, get better breathing, rejet, and install a TAV. I have no need for speed. Thanks everyone!
Torque is king :) I want to bomb hills like there flat when my motors built.
 
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