High compression 350x?

[Liquid-Darkness]

So what kind of compression can I get away with for a Honda 350x? The only source of fuel I will have is 110 race gas and premium gas. I have found that a 350x with a 12:1 wiseco pistion and pure 110 race gas will run real smooth and no predetonation.. What about 13:1? Wiseco makes a piston at 13:1 and I was wondering how high on fourstrokes can I go on compression with just 110 racegas?

[oscarmayer]

should be fine on 110, but you need jetting, porting, and exhaust work to compensate if you have not done so already. your basically going to increase performance by about 7-10% which will be maybe 2-3 hp. something you probably will not feel unless you do lots of extra stuff to support it. that is usually reserved for racing style setups.

[Liquid-Darkness]

Anyone on here do good 4 stroke porting and polishing? What would that cost me? I figure a port & polished head, 13:1 compression on a fresh bore, jetting and a performance exhaust with 12-13/ 40 tooth gearing should give me some extra pep.. Lol I just want the power and torque of a few light mods... I have ran a 12:1 before with simular stuff done to the bike and loved the power.. Its just fun lol..

[rg97]

13:1 will work great with 110, but like oscar said, you'll need other work too to see big performance.
Have fun kicking that over lol...

[Liquid-Darkness]

Lol I know it will be a mule to kick..

[oscarmayer]

you can call Endyn. their website is www.theoldone.com
tell josh mike wichter sent ya.
he does all my special porting work. they use CNC valving work and stuff to port the heads with. I imagine labor will be around $200+ parts and shipping, but they do top notch work. if you send the piston they will probably prep it for you as well so it is ready to install. (yes you have to actually prep pistons before installation otherwise you risk the change of detonation. especially on higher compression engines.)

I bet some of the guys here may be able to do it for a little cheaper. you probably need to look at doing a cam, larger carb, aftermarket exhaust, heavier duty clutch basket and clutch. the list grows more and more to do it "right". your probably gonna look at around $1400+ build when your done. it will run like a raped ape that's for sure if you do actually do it. if not, stay with what you have. if you do not have a cam, and exhaust and bigger carb, that would be your next logical step before going higher compression.

good luck what ever ya do, and keep us posted.

[DohcBikes]

it will run like a raped ape that's for sure if you do actually do it. if not, stay with what you have.

Correct me if I'm wrong Liquid, but I think he's still searching for a trike... may be doin' a little bench racing here?

[Dirtcrasher]

Have a ball. If this is your only trike then enjoy the race gas.

I hate running race gas because I have , Uhmm, just a few built trikes; And keeping fresh race gas around is tough.

I did 12:1 on an 87 200X motor and regret it. I wish I went 11:1 or knew how much to cut the top of the piston off to allow me to run 93 super gas.

The thing is a rocket but too much of a PITA to keep fresh race gas. I gotta tear it down and get the octane level better..............

[Liquid-Darkness]

Yeah I am still looking for a bike.. I am just refreshing my brain about 350x mods from the last time I had a bike. I am just looking ahead if the bike I do get needs a topend, I want to be ready.. At the least, a fresh topend with stock compression and a performance exhaust and jetting, gearing may be all I do.

[BOB MARLIN]

How are your restictions on race gas in that part of California?. I can't even buy it here in so. cal. unless I fill out all kinds of paper work stating I am racing in a "real" racing event and provide info on that event.

[Liquid-Darkness]

Well its been a few years sense I have bought race gas. I hope I don't have to fill out a bunch of crap for race gas, lol. I don't know yet.

[CRAZY70MAN]

How are your restictions on race gas in that part of California?. I can't even buy it here in so. cal. unless I fill out all kinds of paper work stating I am racing in a "real" racing event and provide info on that event.



^^ Unreal????? Were the terrorists buying it is it a ingredient in drug making???? That really sucks.......

[JasonB]

i will throw in more about race gas, its a special trip for me to get some and i kinda regret having switched my 310 over to the stuff. smells good in whatever 2 or 4 stroke application you run it in though lol

[tri again]

I have one hi comp trike that runs great but seems to stay parked.
Just not fun to kick.

[jays375]

If you do any motor mods to the top you have to do the bottom also.That almost 30 year old bottom won't take a beating for very long.

[ScreaminRed]

What if u have 11:1? Do u need to run a mix of race and premium? Ive had major blueing on my pipe b/c of improper jetting from previous owner. I was running 93 at the time and she dropped a valve too. I don't think anything major happened from what I can tell, it just quit running. Didn't seize up luckily. Sorry, I don't want to jack the thread, just a quick answer on the mix for 11:1. :)

[jays375]

More than likely the keeper came loose.You more than likely ruined the guide.That is why when you build up these old motors you need to completely rebuild them.The bluing is a lean issue.

[ScreaminRed]

More than likely the keeper came loose.You more than likely ruined the guide.That is why when you build up these old motors you need to completely rebuild them.The bluing is a lean issue.
Did the keeper come loose b/c of the heat emitted by the lean issue? That's what I was wondering. Anyone on the mix for an 11:1?

[tri again]

Well its been a few years sense I have bought race gas. I hope I don't have to fill out a bunch of crap for race gas, lol. I don't know yet.

Yeah, as with a few other things these days, make sure you have something to feed it before you find you can't.

[tri again]

Did the keeper come loose b/c of the heat emitted by the lean issue? That's what I was wondering. Anyone on the mix for an 11:1?

Now you got me wondering WHY would a keeper come loose?
Sloppy valve guide? or sloppy rocker arm?
Real hard to visualize. I wonder if a valve got stuck open somehow and then hit with the rocker on the next revolution....naaaah. If only Walt Disney had my imagination.

If you do take the head off, which I guess you might have to, make sure you eliminate any sharp edges, like if the valve dinged the piston so it doesn't glow and detonate like whatever that's called, preignition?
Sure hope yours is an easy fix.

[ScreaminRed]

I'm sure the head's coming off, just ain't got to it yet. Only did a visual through the top cover and plug hole. I could see the valve sitting lower, and the keeper looked bad also. I said i didnt want to jack liquid's thread! Sorry man! :) Happy New year!

[barnett468]

How are your restictions on race gas in that part of California?. I can't even buy it here in so. cal. unless I fill out all kinds of paper work stating I am racing in a "real" racing event and provide info on that event.If you live in Orange County Calif., you can simply drive up to the Shell Depot in Santa Ana next to the 55 fwy by 4th or 17th st and get it right from the pump or order it from VP Racing Fuels etc. or go to Lucas in Orange and buy it direct. No paperwork required.

[barnett468]

Searching for a local fixer-uper 350x

Yeah I am still looking for a bike.
Try the following if you haven't yet, craigslist and also call the parts department of local atv shops, they occasionally know where some bikes are.

[Liquid-Darkness]

Yep I scan craigslist every day for a good buy.. The bike shops here in my town are caca lol. Happy Newyears!!

[81Rmachine]

If you're looking to run alot of compression the first thing I'll tell ya is compression and cams go hand in hand. I really cant stress that enough! I know alot of guys running stock cams with 12:1 pistons and its very hard on crankshafts and kickstart mechanisms. I've seen 3 83-85 200x's with broken kickstarter gears because they had a 12:1 piston and no cam to bleed off cranking compression.
We deal with this question at work and while we build V8s the principal remains the same. If a guy calls and wants to build a 350 Chevy with an RV cam with no more than 200 deg of intake duration @.050 and hes running iron heads I'd never suggest anymore than 9:1 on pump gas. Now If he was persistent on 10:1 I'd tell him well you'd better be running race gas or E85 and good luck keeping it cool. In a V8 application too much compression with too small of a cam is very hard on rods and we see alot more rod failures in street stock engines where rules require a stock con rod and milling of the heads. 11:1 compression and stock rods is a recipe for disaster in these engines especially holding 6800 rpm constantly.
Basically the point I'm trying to make is if you want your 350x to run cool and run for a long time, choose your cam and piston accordingly. My XL500S dual sport bike is basically a giant 350x engine, and when I bought it someone had already put a 12:1 wiseco in it with the stock cam and it would lift the head and make a loud crack everytime you gave it full throttle. Kicking it over wasnt an issue due to the factory manual compression release but it ran extremely hot no matter how light of riding I did. I've since rebuilt it, bored and honed the jug as the old piston had .012!!! piston to bore clearance due to a collapsed piston skirt from all the combustion heat. I put in a 1mm over 10.5:1 Wiseco with .002 piston to bore clearance, and ordered the WebCam 402 grind for all around performance which bled off alot more low speed compression and gave the bike much more mid range. I also honed the guides, cut a 5-angle valve job, and did some light porting in the bowl area to compliment the cam. I've just recently ported and machined a head for my brothers 350x while I was working at a race head shop in Wisconsin. Ill post pics and flow numbers if your interested. This one we will be going for a top end engine so its not getting stroked, just bored to clean it up and a healthy cam and 12:1 piston. His rockers will also be getting hard welded and I'll have his springs set up .050 from coil bind to eliminate spring surge at high rpm. Hope this helps, let me know if you have any questions

[Liquid-Darkness]

Yep... I will proly go with a fresh bore on a stock comp pistion.. Will be the cheapest route.. Gearing and an exhaust and I will have plenty of pep..

[6speedthumper]

If I were you, I'd at least put a 10.25:1 Wiseco. Nicer piston, will work fine with stock cam, won't run terribly hot, and it'll give a really nice "hit" on the bottom.

[Liquid-Darkness]

Iv ran a 10:1 before on a 350x.. It had real good power, predetonated a little while backing off full throttle, jetted of course with premium fuel. I just want a fresh topend, compression is not a big deal, would rather keep it lower anyway as my dads 250sxs and vehicals all run on standard gasoline.. Makes fueling up easyer when we stop for gas.

[6speedthumper]

Sounds like it was a tad lean to me, but hey, I don't know the bike either. Lol. But, I understand the whole "fueling up" thing. I have to keep 5-10 gallons of 93 oct for my quads at home.

[Dirtcrasher]

Iv ran a 10:1 before on a 350x.. It had real good power, predetonated a little while backing off full throttle, jetted of course with premium fuel. I just want a fresh topend, compression is not a big deal, would rather keep it lower anyway as my dads 250sxs and vehicals all run on standard gasoline.. Makes fueling up easyer when we stop for gas.

And I see nothing wrong with that; OR running a 12:1 in a 83-85 200X. The stock cranks don't break, the kicker gears in that model are flawed at 9.5:1 so I wouldn't put that in the same category as multiple pistons on one crank.

However, it's a waste to have a high compression piston without a camshaft because they compliment each other and maximize the performance along with a carb, and better flowing intakes and exhausts. High compression doesn't break cranks in single cylinder engines. That's a silly thing to say with thousands of us running stock cranks....

Or OEM cranks with a cam.

[fallguy666]

×2...I run a 12-1 high comp piston.I know its got an aftermarket crank,rod and cam though.I ran a 12-1 on my brute force and my v-force,both on stock cranks....for many,many hard miles.my 350x is not all that hard to kick.even though I don't have a compression release.

[Liquid-Darkness]

Yeah I got some booboos from my old 350xs kicking me back.. Before I learned the trick..Lol.

[81Rmachine]

Compression with no cam to bleed it off is hard on connecting rod bearings and while you may not break a crank your still going to wear out rod bearing prematurely. I have seen galled wrist pin bores from it. If you want to run lots of compression it makes for a very snappy low end but high compression pistons were made to compensate for the compression a large duration cam bleeds off... period. Im not telling you not too just speaking from experience when I didn't know anything, I put a few 12:1s in 200x's without a cam and like I said my 500 already had one and, I wouldn't do it again.

[Liquid-Darkness]

Newyears and a new trike coming in the next two months I hope. :naughty: Gorman OHV next summer for sure..

[Liquid-Darkness]

Yeah I got my 85 350x!! Rings and topend are in great shape, loads of compression and no smoke.. I will run this topend until it will run no more.. Hehehe. Happy Saint Pattys Day!!

[NeverLift]

What if u have 11:1? Do u need to run a mix of race and premium? Ive had major blueing on my pipe b/c of improper jetting from previous owner. I was running 93 at the time and she dropped a valve too. I don't think anything major happened from what I can tell, it just quit running. Didn't seize up luckily. Sorry, I don't want to jack the thread, just a quick answer on the mix for 11:1. :)

I have ran 91, 92, 93 octane (highest the gas station has) on my 440ex 11:1 for 6 years with no issues.