Kyosho Cox .049 Mini Cooper Engine Assembly

If I see it well, rings 60 and 95 both slip on the cylinder and let it be screwed in the crankcase completely, meaning that compression is not affected? Their mounting sequence only changes the vertical position of the muffler?

From the underside of the crankcase to the top of the cylinder with the rings and Exhaust manifold the measurement is 40.5 mm
From the underside of the crankcase to the top of the cylinder without the rings and exhaust manifold the measurement is 40 mm
I have no other engine to compare this to .

I do not know if this has any effect on the performance of the standard engine .

I don't think the correct mounting of the muffler results in the change of the said distance. If the engine is sub piston induction design I.e. the skirt of piston when at top dead center opens the crankcase, then the muffler will already reduce the engine performance that, with reduced compression would further deteriorate.

balogh wrote:I don't think the correct mounting of the muffler results in the change of the said distance. If the engine is sub piston induction design I.e. the skirt of piston when at top dead center opens the crankcase, then the muffler will already reduce the engine performance that, with reduced compression would further deteriorate.

Balogh: maybe the worry is if the parts are assembled incorrect there is exhaust leakage thru the side of the muffler and not thru the muffler. The parts may not seal correctly.

I tried to print the drawing late last night, too late, but couldn’t read anything.

So thanks balogh for finding the parts, where?, and helping the new forum member.

Happydad        

Thanks, Happydad, the way I understood Ted's concern, was that the muffler, when mounted, elevates the cylinder top by 0.5mm as if the cylinder could not fully screw in the crankcase and hence, the compression ratio is reduced.

I doubt it was designed such by Kyosho intentionally, because the muffler itself already robs engine performance due to SPI, and the reduced compression ratio by the elevated cylinder top position would be a second performance robber.

Anyway, I have not seen the Kyosho assembly. The COX parts list I referred to is accessible among the "Instruction Sheets, on the left of this page.

balogh wrote:Thanks, Happydad, the way I understood Ted's concern, was that   the muffler, when mounted, elevates the cylinder top by 0.5mm as if the cylinder could not fully screw in the crankcase and hence, the compression ratio is reduced.

I doubt it was designed such by Kyosho intentionally, because the muffler itself already robs engine performance due to SPI, and the reduced compression ratio by the elevated cylinder top position would be a second performance robber.

Anyway, I have not seen the Kyosho assembly. The COX parts list I referred to is accessible among the "Instruction Sheets, on the left of this page.

Maybe it is gunk, buildup of dried oils and castor oil? The muffler assembly looks tarnished. Is it clean? Has it been cleaned so there are no small particles of gunk on any of the mating surfaces that equal  .5mm? How much is that in inches?  0.02 inches. Possible to be dirt or gunk, but not likely.
   Check to see if there is anything on any of the mating surfaces, gunk, a burr of metal, left over seal pieces, etc. if nothing else you could use .02 inches of shims to be sure the cylinder is tight. You shouldn’t need them, but something is not right.
   Check everything, then check it again. You will find it!

Edit: maybe the stepped washers need to be aligned oppositely, like puzzle pieces. Then they will account for the .5mm, .020inch. MAYBE. Did you look at the way the 2 pieces were oriented?

P.s. where are you from? What country?

Happydad        

Some more pictures



A bit better measurement with the digital , difference now with the maniflold on is .27 mm higher .
Do not know if that will make much difference to the compresion .

GpBear wrote:Some more pictures



A bit better measurement with the digital ,  difference now with the maniflold on is .27 mm higher .
Do not know if that will make much difference to the compresion .

Did you clean the parts and check for burrs on the metal or gunk, pieces of dried oil, castor oil, or seals-gasket pieces loose on the edge of the parts mating. something is hangin up. and what about the step in the 2 rings you mentioned? do they fit together, but opposite like a puzzle? if they are both to 1 side they add in height, but if they are opposite they may fit together and subtract the .27mm????? I would like to se pictures of the 2 pieces you mentioned. It is 1a.m. here so I am out until tomorrow, nice chatting, GpBear.

looks like you need to request a flag my friend. just PM "admin" and say pretty, pretty please can you make a flag for "your country". LOL, It will be a surprise to some. I noticed you posted somewhere.

happydad      

GpBear wrote:...............
A bit better measurement with the digital ,  difference now with the maniflold on is .27 mm higher .
Do not know if that will make much difference to the compresion .

Ted, that 0.27mm difference you measure with and without the muffler and spacer rings still equates the thickness of several head shims stacked on each other and as such, may have a sizeable impact on the compression ratio. (I do not recall the exact shim thickness, but remember one being much thinner than 0.27mm) I would suggest that - as Happydad also points out - check for gunks and burrs, dents etc that add to the stock 40.11mm height measured without the muffler.

happydad wrote:.............

looks like you need to request a flag my friend. just PM "admin" and say pretty, pretty please can you make a flag for "your country". LOL, It will be a surprise to some. I noticed you posted somewhere.

happydad      

Happydad, Ted is Canadian who settled down in the Netherlands... he wrote about it in his intro thread:D

balogh wrote:

happydad wrote:.............

looks like you need to request a flag my friend. just PM "admin" and say pretty, pretty please can you make a flag for "your country". LOL, It will be a surprise to some. I noticed you posted somewhere.

happydad      

Happydad, Ted is Canadian who settled down in the Netherlands... he wrote about it in his intro thread:D

Somehow missed it, but caught the posts about the mini-cooper and muffler issue.

Happydad

An update about this engine .
I have thoroughly cleaned all componenents and packing rings .
There was only a bit of crud aroung the cylinder .
After reassembly I determined that there is still the small difference of increased volume due to the packing rings which hold the maniflod tight in place .
Also not impressed with the compression of this engine when reassembled .

Therefore I have ordered a new Cox PT-19 engine with Car glow plug and spare parts .
About 3 weeks delivery time , I hope .

In the meantime I am going to try and get this old one started on a small bench test stand that I built , hopefully by Sunday .

Would have been sooner , but unfortunitly I have a guest room and inlaws like to visit .

Update to follow .

Ted

GpBear wrote:An update about this engine .
I have thoroughly cleaned all componenents and packing rings .
There was only a bit of crud aroung the cylinder .
After reassembly I determined that there is still the small difference of increased volume due to the packing rings which hold the maniflod tight in place .
Also not impressed with the compression of this engine when reassembled .

Therefore I have ordered a new Cox PT-19 engine with Car glow plug and spare parts .
About 3 weeks delivery time , I hope .

In the meantime I am going to try and get this old one started on a small bench test stand that I built , hopefully by Sunday .

Would have been sooner , but unfortunitly I have a guest room and inlaws like to visit .

Update to follow .

Ted

Ted: have you measured the distance from the top of the “ground” area of the cylinder to the bottom of the “ground” area? Sometimes there is a small variation in that area. I will measure several “ground” cylinders and post here later. I have many of those cylinders and we should see a variation in the lot. Just not sure how much. No guesses, yet.

Happydad

cox engines dont have the compression you think they should have
I myself would describe them as above low or medium
and tuning engines are higer medium or lower high

It is a matter of glow head. My stock red postage backplate 049 reedie spins the 4.5x3.5 APC at 23k on the ground and unloads over 28k in the air. All this with only 20% nitro.
It has a high comp Kamtechnik turbo head on it. I do not think a stock head would bring it above 18k although I never tried.

All:

I took some data on the dimension of the distance from the last heatsink fin to the top of the "berm" that screws ito the crankcase.  see picture:


Measured between these points, lines

here is the data:

ref.        inches.       mm.        O.D of cylinder
1.           .431.         10.96.         .578 in.
2.           .439.         11.15.         .577 in.
3.           .427.         10.84.         .577 in.
4.           .439.         11.17.         .577 in.  #3 cylinder
5.           .431          10.96.         .512 in.   old #2 cylinder , note measurement .065 smaller than other ground
cylinders, very sloppy fit to throttle sleeve

non ground cylinder data for kicks.

6.           .439          11.15.          .580 in.
7.           .433.         11.01.          .580 in.    
8.           .413.         10.59.          .580 in.
9.           .432          11.10.           .580 in.
10.         .441.         11.22.          .580 in.

the variance in the ground cylinders was maximum - 11.17mm  minus  minimum - 10.84mm = .33mm wow
variance in non ground was max. - 11.22mm minus 10.54mm = .68mm wow, wow.

and you were worried about what .21mm was it?  the variance in the ground area is larger than your .21mm ???

maybe your idea of another engine was o/k. , but you should look at the ground area, or the area between the last fin and the bottom of the berm as seen in the photo and try to find one with a larger distance.

hope this data helps someone. if there are errors, please PM me so i can correct them. I'm old and make mistakes and i can't find my glasses. But i measured each cylinder several times and o both sided and took the average measurement. also tried to measure in a perpendicular line to the cylinder to keep the distance true and not at an angle.

happydad.

Great data!

If I had designed the COX cylinders I would have set the strict tolerance on the distance between the top dead center inside (where the head shim sits), and the bottom of the ring on which the cylinder bottoms out when screwed in the crankcase, because this distance influences the stock compression ratio. I do not think the lowermost fin on the cylinder had a strict position tolerance as that has no influence on the top dead center position of the piston relative to the horizontal axis of the crankcase. Hence the wide range of measurement data.Sorry if my explanation is confusing.

GPB,

Any chance you have that bottom plate on upside down? If you flip it over so the flat is on the block, you may gain your compression/reduced overall deck height. The way the bottom plate is now will cause the muffler assembly to stand up a bit higher from the crank center line, this reducing compression and making the cylinder overall height taller.

Try it and see if the muffler will then have too much slack and rattle.

GpBear wrote:Some more pictures
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944_Jim wrote:GPB,

Any chance you have that bottom plate on upside down? If you flip it over so the flat is on the block, you may gain your compression/reduced overall deck height. The way the bottom plate is now will cause the muffler assembly to stand up a bit higher from the crank center line, this reducing compression and making the cylinder overall height taller.

Try it and see if the muffler will then have too much slack and rattle.

GpBear wrote:Some more pictures
[

944_Jim:  Funny, I was just thinking the exact same thing. I saw the email with “Kyosho...”, selected it and was staring at the pic and read your comment.
I think I read somewhere above he tried it both ways, but I’m old and forget things.

HD.

nope its the correct way
because you need a small bit of room for the starter spring
also I was one of the old owners of the car he is restoring
(back in 2015)