Highest compression ?

[thebig450es]

Ive been searching on this topic for awhile now, you usally see, 11:1, then 12.5:1, what do you think the highest the 400 could handle, I found some 137 octane fuel at about $18 a gallon lol. You would need a Hot Rods crank and some roll tap HD head studs. Ive heard about someone having 14:1, but how much power do you really make, i think you could go to a stage 3 cam then. Just throwing some off the wall thoughts out.

[flyboy1294]

Originally posted by thebig450es
Ive been searching on this topic for awhile now, you usally see, 11:1, then 12.5:1, what do you think the highest the 400 could handle, I found some 137 octane fuel at about $18 a gallon lol. You would need a Hot Rods crank and some roll tap HD head studs. Ive heard about someone having 14:1, but how much power do you really make, i think you could go to a stage 3 cam then. Just throwing some off the wall thoughts out.

I've heard of a 300ex having a 14:1 before, but the thing literally melted because of temperature issues.

I've got a JE 13:1 in my 440 at the moment. I haven't seen any production pistons with higher compression than that. However, I think I saw a guy that made a custom piston for his that was 16:1 or maybe higher... I'll see if I can find it.

[thebig450es]

If you used a FST cooler and SPAL fan and air scoops you should be able to cool it pretty well, and the racing fuel will help on heat and det. I wonder what the weakest links would be after the crank and head studs. I personally am not planning on going wild with the compression but just trying to have some fun and learn alittle lol

[flyboy1294]

I haven't had any real cooling issues with my 440. It over-heated once on a trail-ride, but I was trying to crawl up the face of a rock cliff in 1st gear for about 2 hours lol. I think any air-cooled engine would have over--heated. But with air-scoops and a SPAL you should be good. If you want to do the aux. cooler then it will help all the more.

And I searched for that one guy with the custom 16:1 stroker in his ex and I got nothing. Maybe someone else will remember him? I think the thread had something to do with putting an Xr400 kicker on an ex (The guy had done this..)

[thebig450es]

I wonder what 16:1 would feel on a 400 lol, Even 14:1 should have great torque gains over stock.

[flyboy1294]

Originally posted by thebig450es
I wonder what 16:1 would feel on a 400 lol, Even 14:1 should have great torque gains over stock.

I've driven a friends 11:1 440, and it is disappointing compared to mine :D I am willing to bet the 14:1 would be considerably stronger...

[thebig450es]

What all to do have done to your 400, i see its a 440 13:1 with a stg 2 cam

[Snipe]

I know the guy your talking about, its the guy who first started the XR kickstart conversion on the 400ex. He had a custome made 15:1 piston. He had it stroked as well and then lightend the flywheel 2.2lbs and installed the kickstart and removed all things electric start.

His only problem he had was clutches. The clutch couldnt hold the motor back every afterket he tried failed and the only thing he could get to work was the OEM clutch and then it wore out pretty quick. But im sure every bike would be diferent.

[flyboy1294]

Originally posted by thebig450es
What all to do have done to your 400, i see its a 440 13:1 with a stg 2 cam

I didn't do the work with the engine myself, I bought it freshly rebuilt actually.
But, it does have a 13:1 JE 440 piston, I run it on 110 octane, its got a stage 2 hotcam, full DG exahust (pos, but its better than stock...) and I got a 450r carb ready to be installed, and then I put the K&n filter and EHS lid on it. I think it has an HD clutch setup, and a fly racing perch. Performance wise, that's all that I can remember.

It's actually alot more powerful than my friends stock 400, and I don't even have the carb on it. And its never given me any reliability issues. So I can't complain.

Before hot weather comes back I am going to try to get SPAL fan and airscoops for cooling.

[flyboy1294]

Originally posted by Snipe
I know the guy your talking about, its the guy who first started the XR kickstart conversion on the 400ex. He had a custome made 15:1 piston. He had it stroked as well and then lightend the flywheel 2.2lbs and installed the kickstart and removed all things electric start.

His only problem he had was clutches. The clutch couldnt hold the motor back every afterket he tried failed and the only thing he could get to work was the OEM clutch and then it wore out pretty quick. But im sure every bike would be diferent.

Yep that's him snipe. I skimmed over the thread but didn't really pay much attention to it. Is the guy still on here much anymore?