I have an 1984 Honda 200S which may or may not have a 185 engine on it. The Honda dealer said the carb appears to have come off a an older 185S because of the push in verses screw in idle jet. That may or may not be true and carbs can be easily swapped but it has given me reason wonder. Which ever motor it is, 185 or 200, it is in need of a top end rebuild among other things but it does run. I also have a 200S engine in pieces in a box, or at least the guy I got it from said it was a 200.

How can I tell for sure what I have? Will the jug from a 200 fit on a 185 bottom half? How about the heads? Can I put a 200 head on a 185 cylinder or visa versa without having compression problems?

My plan is to have the spare 200 cylinder punched out to the next oversize and rework the head. That way I can have all my parts ready to bolt on without putting the bike out of service. But I don't want to throw money away on a piston kit and having the cylinder bored if it isn't compatable with my lower engine. Any advise would be appreciated.

 

I THINK the bottom ends are the same... I would say that your top end from the 200 would fit. I would not switch the heads on them though. I would keep the 200 head with the 200 cylinder and the 185 with the 185 head...

This is just my best guess. I know there are alot of people on here that know for sure.

 

Thanks Mr ATcRoxz. Once I learn how to ID these motors I will try not to mix up the cylinder heads.

I recall reading a thread somewhere - may have been on another site - from a dude who had put a wrong head on a 185 and ended up with WAY too much compression. Seems like he said it ran like a scalded ape but it took King Kong to pull the starter rope.

Hopefully I will hear from some of the other Guru's. I still need to know how to visually tell these motors apart.

Thanks again for the responce!

 

on the bottom back of the cyl is 179cm or 198 cm the smaller is for a 185, the larger is for the 200 the cam is a little higher duration for the 185 hence, slightly more compression than the 200. You need the compression release for the 185 head on a 200 it will pull your shoulder apart because of the increase in compression. the heads are the same the cam is the big difference in the 2 top ends. If you really want to rip your shoulder apart use an xr200r cam or a 185 dirt bike cam in your 185/200 conversion

 

Thanks for the info. I'll check the cylinders tonight. But I'm not sure I understand about the cam/compression thing. The cam shouldn't have anything to do with compression, right? That comes from the profile of the piston in conjunction with the combustion chamber dish size in the head. The cam will dictate when the valves opens, how long they stay open, and how far they open, but won't effect the actual compression ratio. Or at last that is my understanding.

So it sounds like a 185 head on a 200 cylinder might be a rope breakin combination, but a 185 cam in a 200 motor might be a performance booster?

Anyone with some further thoughts? I need all the help I can get.

 

Yes the cam has ALOT to do with compression... the longer the intake stays open the more air the motor will take in and then you will have more air to compress making the compression higher. The heads are the same... the cams are the differences. The 200s cam has more duration in it then the 185. If you want real performance out of a cam you need to get an xr200r cam, or a 185 cam out of a dirtbike just like oldkawi said...

 

There were only 2 cams used on any of the 185 and 200 trikes. You had the 200X cam and then the cam used in ALL the other models.

Cylinder heads are also the same. No difference in compression, porting, valve size,....no differences.

The compression difference has to do with the dish used in the tops of the FACTORY pistons. Most of the aftermarket pistons use the same dish, so no big deal. This shouldn't be a concern anyway though unless you are using a piston with a "dome". And even then, you will have to be well above the 10:0 range to cause a clearance issue with the valves using a stock cam.
Go to switching cams and using high compression pistons though, and you will want to make clearance precautions.

As for these parts working on your 185 (or 200) bottom end, you will into no issues whatsoever. Just match pistons with cylinders ofcourse.

 

I'm backing Knowsalot on this one 100%

These other guys need to do a touch of research. [img]i/expressions/face-icon-small-happy.gif[/img]

 

I appreciate everyone’s input. Last night I looked at the base of the cylinder on my trike and on the spare parts motor. The one on my scooter read 192 I think - it was hard to see. The spare cylinder read 180. That doesn't match the numbers posted before. So is one considered a 200 and the other a 185? Correct?

I’m told there’s no substitute for cubic inches (or in this case cubic centimeters) so I guess my best bet for performance and torque would be to stay with the 200 and have it bored to the next oversize. Is there enough meat on a 185 cylinder to make it a 200 or can you really tell much difference between the two? I hate pulling the running motor apart when there are just a few weeks left of summer vacation for my son. He lives to ride that old Honda but I am about to have to do something. It’s going to give up the ghost pretty soon any way you slice it.

And finally, concerning the compression ratio cam question/issue thing, my goal is to avoid assembling dissimilar parts and ruining something. I haven't yanked the head on the motor on my bike so I don't know if the piston is domed or not. The other one is a flat top. Looks like there is no risk screwing up as long as I have the right piston jug combination and stock pistons. But you guys make an interesting point. While I agree with Knowsitall that compression ratio is a measure of the volume in a cylinder when the piston is all the way down at the bottom of it’s stroke as compared to how much is left when the piston is all the way at the top, and that this ratio remains the same regardless of the camshaft configuration, a performance cam does let in a larger volume of the fuel air charge. There would almost certainly be more vapor to compress over a stock setup. Logically that would equate to slightly higher combustion pressures if not compression. Not compression ratio, but actual compression. Perhaps the difference would be too slight to feel with the pull rope, but I’m thinking there would be a difference. I’ve never looked at it that way until now. It’s given me a headache….

Thanks again to all for your input and advice. I look forward to hearing back from you.
Ride safe!

 

Ooops -sorry mister KNOWSALOT. I think I referd to you as "Knowsitall." It was a slip of the finger. If it makes you feel any better you can refer to me as "Texan" rather then "Arkie." But please, don't do it more then once....