200cc engine build......

[Gabriel]

I have two other projects to finish first but I am slowly planning yet ANOTHER build. I keep getting braver each time. LOL!!


What I WANT to build is:
ATC200M bottom end
XR/Xl top end
10.5 - 11.0 to 1 ...just shy of needing better than pump gas
Custom ground cam
XR/XL crank with the heavier duty con-rod


Each engine I build, I get a little better at it. I REALLY wanna plan this one out as far as possible to prevent costly mistakes. I want the M bottom end for the electric start. I have an E bottom but you cannot change the front sprocket out to a different pitch AND it requires a notched frame for the sub transmission which is just weight and moving parts I do not need.

I have read that stroking these engines is pretty detrimental to their reliability. Anyone know if that's true?
I found a website a while back where a guy is making stroker cranks from stock cores. He makes a lot of big bore kits and custom work but for the life of me I cannot find the website. It wasn't a very big or flashy website. Damn! Shoulda bookmarked that.


Big bore kits on 200cc engines have been hashed out and beaten to death. I understand why it's not really possible. No need to cover that but I was curious if someone with a Bridgeport could bore the case to accept a larger sleeve. Probably not worth the effort.

Anyway, thoughts on what direction to go on this engine?
Fabiodriven has inspired me and it is my intention to find an XL200r or even an xl185 (should be the same) titled frame and marry it to an '84 200x to make a street legal trike. The M bottom end with electric start, pull backup seems like the perfect candidate. Will have to do some frame mods, but that's no big deal to me.
As I said, I have other fish to fry at the moment but the more I think on this, the more I feel I MUST build this! I love 200 engines, have a pretty good grasp on them and TONS of parts.
It's worth mentioning, I had 84 XL200R as a teenager. It had 3K (ish) miles on it when I got it at 14 yrs old. Got my learners permit and starting riding it. I had very strict parents, I was NOT allowed to leave the city limits of our little podunk town and I had a curfew of 9pm when I was on the bike. I sold it when I graduated and it had over 49K and still ran like a brand new bike.
I can't think of a cooler build than a basturd child bred from my love of 3 wheelers and a childhood bike. LOL!!!

[greenhuman]

I sell stepped stroker crank pins for 200 engines. They have a step of 4mm which increases the stroke to nearly 66mm. You can then use a CRF230 piston kit ( standard or high comp). These pistons are 4mm lower than the 200 piston which means no cylinder spacers etc. Depending on the bore size, 67mm for example, you end up with 235cc's.
Reliability is not an issue.

[Gabriel]

Aww man! You’re on the other side of the planet!
I’m assuming you would need a core? That’d be costly. Gotta pay to play though.

I don’t fully understand what’s involved in what you’re doing but it seems like you could provide the stepped crank pin and I could assemble it. How wrong am I in that assumption?

[Dirtcrasher]

Case boring - As an example. I have a 350X that is sleeved to a 452CC. It uses a 93mm Wossner piston (I believe that's the size), a Halls Performance ported head, Race cam, XR400/SuperTrapp Can exhaust and a 41mm FCR carburetor.

I had to build an intake for the carb to fit properly.

Anyhow, seeing that I have a few crate motors laying around, I just tore 1 down to nothing, sandblasted off the OEM finish :lol: and PC'd the motor. Then, I stuck it in my Bridgeport mill and bored the cases out about 8 - 10mm larger to accept the thicker sleeve.

By boring them, it accepts a fatter walled sleeve, which is far better than boring the snot out of OEM and "RUN IT!!"...

Some motors can be bored HUGE! But then the cylinder wall is only about 1.5mm's or .060 thousandths, that's too saall. In time it will get hot, crack and fall into your lower end thus destroying your NOS motor...

[greenhuman]

No core needed. You really only need the stepped pin. Everything else you can source there. Get a shop to pull your crank apart and reassemble it with the new stepped pin. The pin increases the stroke by 4mm. You can then use a CRF230 piston to get the correct deck height.

[oldskool83]

Just wondering how strong a 200E stater is for all those mods. Another way is use stock rods and light pistons but deck heads, with port and polish. Keeping weight off the bottom end internals. I've done it before with great gains, very great gains.