Arc billet flywheel??

M

mteezey

New Member
#1
#1
I got a Briggs raptor built by jerry dover. It runs on methanol I know a little about it like bored .010 over, billet rod, dyno cam(not sure on size). Anyways I decided to hook a tach up to see what kind of rpms I was getting. And I've hit 6100+ a few times without feeling like I was being too hard on it. :eek: Anyways I'm trying to figure out if I should go get the billet flywheel and maybe advance timing key. Just wanted see if everyone thinks it's a must to go billet on a Briggs at that rpm. I do know it's the safest way from no matter what angle you look at it. But is it a must ......

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M

mteezey

New Member
#4
#4
Thanks. I think im gonna go pull the cover off and see whats going on inside that bad boy before i make my decision. Whats your thoughts on performance to go along with the billet flywheel. I always looked at it like a heavier flywheel will keep the momentum better. But alot of my buddies swear that they increase horsepower(i dont see the logic). But i cant seem to find any info that actually says it does or doesnt. I guess i can see how it can rev quicker ect but actually gaining horsepower from it....:confused:
Maybe if i get her done today i can take her down by the airport and really see:scooter:
 
B

bpoirier

Member
#5
#5
We run our stock class flatheads up to 6800-7000rpm with the stock cast iron flywheel no problem. It's a rule in the stock class you cannot run a billet flywheel. Dover makes great race engines. It probably already has a advanced key in it.
 
M

mteezey

New Member
#6
#6
Yea it did have an advance key already. If I would of pulled the flywheel off before asking I could of saved from even having to start this thread. So now I have a billet flywheel with the same 6 degrees advance timing key Dover put in.

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M

mteezey

New Member
#7
#7
ok so i have my new flywheel installed and now i cant ride it for more than 20 minutes without fouling out the plug. I have removed the flywheel to make sure the timing was right. I t already had a 6 degree advanced key in it. And ran like a champ with the stock cast iron flywheel. Ive played with the jet thinking it was getting too much fuel(methanol) but nothing i have done seems to be helping at this point. Does anyone have any suggestions for me? Maybe remove key since flywheel is tapered and try timing it different? Gonna try the stock jet out of another carb i got and see if that helps at all. :shrug:
 
creia

creia

#8
#8
6 degrees advanced seems like too much for that engine, and could be causing your fouling. I believe that 2-3 degrees would be more typical.
Michael
 
B

bpoirier

Member
#9
#9
What size jet do you have in it now? How many turns out do you have the mixture screw? I would probably run a 46-48 jet with the mix screw 1 1/2 turns out. You may want to change to a less advanced timing key too. Maybe a number 3 key would better for your application. Make sure the carb to block screws are tight and the gasket is good. Also check the fuel tank to carb screws and gasket there as well. Double check the air gap on the coil too. The big thing with our flathead engines is getting enough heat in the cylinder head. Most of the time we tape up the grill on the side cover to help get the heat built up in the head. We like to see 400-425 degrees on the CHT in race mode. Your not going to build as much heat if you are just putting around.
 
M

mteezey

New Member
#10
#10
It has a 49 jet in it now(at least thats whats engraved in the face of it). And i have the mix screw about 2 1/2 to 3 turns out I set it where it seems to run the best. Im gonna go through this motor once it gets a little cooler up here. Since everytime i look closer at it i noitice more stuff on it. One thing being i looks like the builder modified a 3 or 3 1/2 horse carb and modified the block to be able to bolt it on. Everyone in the kart world i have spoke with says that the builder of the motor is one of the best in the country so im sure theres a good reason behind that. Im just getting back into the whole small engine thing since mini bikes are making a big comeback up here and it was my favorite thing as a child to wrench on with my pops. Anyways i went ahead and removed the adavanced timing key and set it to more like 2 degrees so with the 2 degree advance the arc flywheel has built in it puts me at 4. It seemed to run a little better like that. And i actually was able to get a couple more mph with the setup like this. The bike went 51 with the old flywheel at 6 degrees and she went 53 now. Not sure how happy i am with he lighter flywheel though i can feel it lose momentum once i get up to top speed where before it would just keep screamin. :scooter: I think alot of the issue withthe fouling of the plugs may be based on weather/humidity. If i run it on a dry day it seems to run flawless but let it be cold and humid and it will foul out the plug. I also noticed some oil on the piston so maybe bad rings adding to it. Im gonna check around at local machine shops to see about going up a size in piston if not just gonna try to hone it and get new rings and see if that seals it up.
 
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B

bpoirier

Member
#11
#11
Glad you got it running better. If it's a raptor carb it will look on the small size. Most of our kart racing engines don't idle all that well but they run great wide open which is really where they are set up to run best. The heavy stock flywheel will definitely help with momentum. I'm sure the light flywheel helps it spin up very quickly. Have you had a tach on it? I'd sure like to know how many rpm's you are turning. I would suggest boring it out and installing a new piston and rings. It's also a good idea to put new rods bearing, rod bolts and valve springs as well.
On a side note I grew up in Detroit, MI. I haven't been up there in a few years. I need to make a trip up and visit my family.
 
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