How about a nice 350x 502cc big bore kit?

[Mickey Dunlap]

I know there were some guys building some big 350x 's on here years ago but they had big dome piston with super high compression that looked like rod breakers to me. I'm building a 502cc kit to run a big cam but on pump gas and I was wanting some feed back if those guys motors stayed together, or if anyone had one them selves and what they thought about them.

[xrider]

There have been tons of setups over the years. The more recent I remember was a 492cc big bore that a member was offering a while back (96mm bore I believe). Another popular one was the Ascott 500 head setup. I can't help you out much on the really big cc motors out there. I am running the 425cc kit that you used to offer in my 350x and it has been bullet proof so far. Easy to start with the FCR carb and 40 hp on tap.

[Mickey Dunlap]

There have been tons of setups over the years. The more recent I remember was a 492cc big bore that a member was offering a while back (96mm bore I believe). Another popular one was the Ascott 500 head setup. I can't help you out much on the really big cc motors out there. I am running the 425cc kit that you used to offer in my 350x and it has been bullet proof so far. Easy to start with the FCR carb and 40 hp on tap.

Well I know about using the Ascot head because I did a magazine article on that back in the 90's in Dirt Wheels. I have built about every bore and stroke combo over the years and I like flat top big pistons with the small combustion chamber of the 350x that keeps a good quench area around the out side of the piston with a short flame travel and light weight pistons. This is easy on the rod and keep the reliability and longevity we all like our Honda's for in the first place.

[big specht]

My buddy has one in a pulling bike that is bored and stroked to 502 with a turbo on it now and it has held up for a long time now it's been turbo charged for a year or so with no problems yet and was n/a for probley 10 year with no problems other than clutch issues.

[oscarmayer]

sounds like an awesome idea Mickey. would be an awesome setup for an MX or CX motor. ;)

[Mickey Dunlap]

My buddy has one in a pulling bike that is bored and stroked to 502 with a turbo on it now and it has held up for a long time now it's been turbo charged for a year or so with no problems yet and was n/a for probley 10 year with no problems other than clutch issues.


How much boost, and was it a stock rod? Compression ratio?

[Mickey Dunlap]

sounds like an awesome idea Mickey. would be an awesome setup for an MX or CX motor. ;)

They are coming. Now I have to go buy a 350x too. lol More because of the new fenders I'm making, they look so cool on the 350x.

[big specht]

How much boost, and was it a stock rod? Compression ratio?

Not sure on compression ratio. It's a 9mm poweroll stroker. As for boost I'm not sure where it's at now but I'm pretty sure it's between 10 to 15psi (we know it's a time bomb)

[TheRealFatShady]

They are coming. Now I have to go buy a 350x too. lol More because of the new fenders I'm making, they look so cool on the 350x.

They'll look even cooler when they're flying by on a 350x with one of your big bore kits!

[BOB MARLIN]

How much H.P increase over stock would this "502" be? One of my 350x's is in dire need of a rebuild and I might go in the direction of a big bore.

[oscarmayer]

well I am getting a 2nd 350x soon, if you want, I am willing to work out a deal. you use it as a test model for a couple of months or so and do the stuff you want. that saves you the $ on buying the 350x. ya just pay for shipping.

[Mickey Dunlap]

How much H.P increase over stock would this "502" be? One of my 350x's is in dire need of a rebuild and I might go in the direction of a big bore.

With the new cams and head work, carb and good pipe it's over 50 with the smaller motors I have been building, but most won't do all that so I'll just put the kit with a cam and a 400ex carb and dyno it the way most will build them.

[Mickey Dunlap]

well I am getting a 2nd 350x soon, if you want, I am willing to work out a deal. you use it as a test model for a couple of months or so and do the stuff you want. that saves you the $ on buying the 350x. ya just pay for shipping.

I have had a few of those offers but I think I would like to build one for my self with the right set up to go fast, cut tank, long swing arm and of coarse low fenders.

[BOB MARLIN]

Have you set a time frame on when this might happen ?.

[oscarmayer]

sweet! ok sounds good sir.

[ama009]

This sounds like an awesome idea!! I am very interested in this. If the dependability is close to stock, i am in!!

[Mickey Dunlap]

Have you set a time frame on when this might happen ?.

The order went in yesterday, so I would say I will have pistons in 10 days.

[oscarmayer]

Mickey,
do you also stroke the engine or just a BB setup with custom sleeve?
what all will the kit entail? I am curious as to what parts will be included, and what is the price range for this kit?

[Mickey Dunlap]

Mickey,
do you also stroke the engine or just a BB setup with custom sleeve?
what all will the kit entail? I am curious as to what parts will be included, and what is the price range for this kit?

It's just the big bore, these engines didn't like to rev with the strokers and the strokers broke, so it's just a bore kit for $350. Re-sleeve the cylinder and bore the cases.

[TheRealFatShady]

Mickey I'd love to run one of these in my TRX300 I'll be using a stock trx350d crankshaft and cylinder/head. These kits should work, but do you know if the clutch will hold up? If not I'll have to swap the clutch basket gear and primary for a reduction. But I'd still need a cam made. Would those be available? No real rush on it, hoping to do this summer.

[Mickey Dunlap]

Mickey I'd love to run one of these in my TRX300 I'll be using a stock trx350d crankshaft and cylinder/head. These kits should work, but do you know if the clutch will hold up? If not I'll have to swap the clutch basket gear and primary for a reduction. But I'd still need a cam made. Would those be available? No real rush on it, hoping to do this summer.

I have HD clutch springs that hold up to my 420 stroker/ big bore for the TRX 300, but I don't know about the 500cc. I can build the cam too.

[oscarmayer]

ok perfect! sounds good sir!

[HairyJR]

Well I know about using the Ascot head because I did a magazine article on that back in the 90's in Dirt Wheels...


Mickey I don't mean to muddy up or change the subject of your thread, but I'd like to read the article you mentioned, can you give a better time frame maybe month or year. Took me a while to figure out that 97mm is the piston size to achieve 502cc. Is it cast or forged?

"HJ" :beer

[Mickey Dunlap]

Mickey I don't mean to muddy up or change the subject of your thread, but I'd like to read the article you mentioned, can you give a better time frame maybe month or year. Took me a while to figure out that 97mm is the piston size to achieve 502cc. Is it cast or forged?

"HJ" :beer

I lost all those mags in the flood here in Hyndman PA.

The 502cc piston is forged with very deep valve pockets for my cam.

[HairyJR]

I lost all those mags in the flood here in Hyndman PA....

hoped you could narrow the month or year in my search for the article, I have a few '90s magazines and have been paging through them trying to located the article.
I'll keep looking but if someone can help let me know.

"HJ" :beer

[Mickey Dunlap]

hoped you could narrow the month or year in my search for the article, I have a few '90s magazines and have been paging through them trying to located the article.
I'll keep looking but if someone can help let me know.

"HJ" :beer

It's on the cover,in a white 250r with red frame.

[ride red #1]

Mickey,
Is there a pipe you sell or recommend for this big bore engine?
Thanks.

[Mickey Dunlap]

Mickey,
Is there a pipe you sell or recommend for this big bore engine?
Thanks.

I think some one on here makes some but it would be for a big valve motor, the head pipe is pretty big. Another member bought one for pretty much a mild motor and he wasn't happy with it. Maybe he will speak up because I told him to buy it with out know what was done to his motor. Or just make a post about big bore pipes for 350x's.

[ride red #1]

I think some one on here makes some but it would be for a big valve motor, the head pipe is pretty big. Another member bought one for pretty much a mild motor and he wasn't happy with it. Maybe he will speak up because I told him to buy it with out know what was done to his motor. Or just make a post about big bore pipes for 350x's.


Will do. Looking forward to your build. Thanks for info.