Just a question

[MoreHP68]

Just bought a 308 grind cam and 22 Ib springs. Do any of you think my stock bottom end can handle 8,500 rpm? should I get a Billet rod and flywheel?

 

[MO Predator Racer]

Definitly a billet rod and then if you keep stock flywheel and turn 8500 you will easily throw magnet. Put billet rod and flywheel on it for sure.

 

[MoreHP68]

 

[MoreHP68]

Do you know the length of a stock rod?

 

[MO Predator Racer]

3.303 is the Standard OHV Clone length listed on ARC's website
https://www.arcracing.com/6270-arc-rod-honda-gx200-std-ohv-3-303-x-1-183-x-709/

 

[MoreHP68]

I appreciate it, thanks!

 

[1fasttiller]

8500 requires some good parts... these chinese recycled beer can engines are capped out at about 7000-7100rpm.

 

[flattop1]

No doubt 8500 rpm .
Requires carrying a broom and dust pan

 

[MoreHP68]

Can the block and stock crank handle it?

 

[MO Predator Racer]

Can the block and stock crank handle it?

Yes. That being said on a predaotr or clone you cant go 3inch bore and ecspect the block to stay together it just isn't practical. I believe you can get somewhere around 2.83 bore or something like that but the moment you go any larger it is just a ticking time bomb. I have seen stock cranks hold 25plus hp.

 

[MO Predator Racer]

Also if using stock crank it would be a wise idea to have everything balanced that rotates on the engine including crank.

 

[MoreHP68]

Good to know, this is all great helpful information. I ask because I am trying to build a badass little clone for Auto X and test and tune days at my local track. I would like to get around 20 hp in the end.

 

[MoreHP68]

My next mod is a 24mm Makuni slide carb.

 

[sundog]

Your rocker arms will be the next to go.

 

[MO Predator Racer]

For a cam and carb like that wanting to turn that rpm...do some head work, port and polish, bigger valves and stuff like that will really help with big carb and cam.

 

[mike97760]

Id be concerned with the 22 pound springs. I would use the 26# units.

 

[mike97760]

Also if using stock crank it would be a wise idea to have everything balanced that rotates on the engine including crank.

Seems like I have read that you cant truly balance a single cylinder engine. There are a lot of posts concerning this on Bobs.

 

[flattop1]

True .

 

[MoreHP68]

For a cam and carb like that wanting to turn that rpm...do some head work, port and polish, bigger valves and stuff like that will really help with big carb and cam.

I have already done some headwork. I am just going to run the 22 springs and wait to put my cam in until I get the flywheel and rod.

 

[MoreHP68]

Ran into a problem........ After I put the springs in I tried to start the motor. My pull cord broke, do any of you know where to find a replacement? I would have rewrapped the thing but it is too old and beat to do so.