185 Piston ring end gap!!

[Atc2484]

Hey guys I am thinking about doing a top end rebuild on my 83 Honda atc 185 s. I didn'nt get the compression because the spark plug hole is too small for my compression tester. But I just Checked the two top piston ring end gaps and they were too big for my tool, there was plenty of play with a 1.14 mm or .045 gauge. Does anyone know what the gap should be? And what size of oversized piston kit would you guys recommend? Thanks for any help with this project.

[MonroeMike]

http://www.3wheelerworld.com/showthread.php?126290-ATC185-200-Service-Data

[Dirtcrasher]

I hate when it's too big for my tool!! :D

I believe the usual rule is .004"s per 1" of bore, or a 3" bore as an example would have a .012 end gap.........

[tri again]

yeah, just stagger the end gaps so the oil has no direct route to shoot up through them all.

Dad an I had the top of a piston come off,
at 1200 feet.
Think it was a Lycoming aviation engine which was overhauled by
an faa certified mechanic.

They grounded ALL those engines until they figured out that the mechanic
set the end gap too tight.

(oops)

We landed uphill under a powerline.

My biggest fear is that I died and don't know it.
This could all be a dream.

;-)

[Atc2484]

I noticed the exaust from the engine was kind of smoky and it leaves black oily stuff over everything around the exaust pipe could this be because of the ring end gaps being to large , and the oil get through them all and burns? Or is it because of bad seals in the bottom end?

[Dirtcrasher]

Sounds like it's just time for a rebuild. It's a thumper so the bottom end seals have no effect.......

[Atc2484]

Sounds like it's just time for a rebuild. It's a thumper so the bottom end seals have no effect.......

So the piston ring gaps are the oil burning problem?

[Dirtcrasher]

Piston ring gaps don't get that large unless the whole top end needs freshening up..........

You may need valve seals and or guides too, who knows.

Get out your wallet :lol:

[Atc2484]

Piston ring gaps don't get that large unless the whole top end needs freshening up..........

You may need valve seals and or guides too, who knows.

Get out your wallet :lol:

Sorry I don't know much but what is a guide?

[WilliamJ]

Its not just the gaps (and those gaps are big) they probably are not sealing well - sloppy in the ring grooves, lost their tension, bores worn etc.

Valve guides. If the valve has more than 3 or 4 thou oil will get sucked down the inlet valve guide when you come off throttle. Sometimes the valves are fine but the guides are really worn, but unless they have no measurable wear then replace the valves as well as the guides and seals. The seats should be re-cut after fitting new guides.
Bill

[tri again]

yeah, I have a cool 90 that runs GREAT but smokes on deceleration.

I think I saw one valve guide seal on the exhaust valve guide in bikebandit parts fiche.
Looks like a rubber seal.

A compression check should tell you if the compression is low
and a squirt of oil in the cylinder and recheck will tell you if the rings are worn
(if the compression comes up noticably)
or if a ring is broken., it won't come up.

Valve guides, or seals if it has them, will smoke in decel because the engine vacuum goes (all the way) up.

does it start and run good?
fouling plugs?
black smoke or blue?

[Atc2484]

yeah, I have a cool 90 that runs GREAT but smokes on deceleration.

I think I saw one valve guide seal on the exhaust valve guide in bikebandit parts fiche.
Looks like a rubber seal.

A compression check should tell you if the compression is low
and a squirt of oil in the cylinder and recheck will tell you if the rings are worn
(if the compression comes up noticably)
or if a ring is broken., it won't come up.

Valve guides, or seals if it has them, will smoke in decel because the engine vacuum goes (all the way) up.

does it start and run good?
fouling plugs?
black smoke or blue?

i already took the engine apart so i can't do a compression test, but with ring gaps that big i'm gessing it was quite low. It does start but only with the perfect amount of fuel in the tank, i don't know whats wrong but if there is to much fuel in the tank fuel comes out of the carb throat, and if i open the carb overflow valve it poors out of that. After every run i have to clean the plugs because they are all black and oily. the smoke is a blue color. also after about five minuites of running the engine idle speed picks up quite a bit on it's own and it starts smoking alot more.

[muthey]

well I can tell you one thing with the fuel issue, check your float and the float needle and seat looking at a sealing problem as that fuel is gravity fed. I just had to replace an o-ring on my 225 dx float seat and was having the same issue. If you are doing rings you might as well do the valve stem seals as well, gotta remember 28 yr old machine and I find most hondas were ran to death. Just my 2 cents

[tri again]

x2 on the float valve .

May also be part of the reason it's fouling plugs..too much fuel.
Blue smoke is usually oil so you may have more than one issue.

I'd be tempted to get a set of standard rings for 10 bucks, hone the bore and
call it good, but that's just me and my lazy approach to reality.

Did you happen to see a little rubber hat on top of the exhaust valve guide?

Maybe you haven't gotten that far yet?
Guides can maybe be 'knurled' if they are loose and wobbly.
It's almost like they thread them internally and then ream them in order to decrease the internal diameter
so the valves ride tighter and less chance of oil blow by.

Easier, faster and cheaper than changing guides.