two stroke rings - which way around?

[motorbyclist]

Right, I'm currently doing a top-end rebuild on my '86 honda H100s (same motor as the MB100) and have become somewhat confuddled...

the two rings look identical, and have no marks to suggest otherwise. The only way i have to put them the right way up is the keystone shape, but there's nothing to tell which one goes on top...

my four stroke experience tells me there is a difference between top and bottom ring - is it the same for a two stroke or are they infact identical top/bottom rings?

Attached is a pic of what i've (apparently) got and how i understand the forces to act....

(there is an octagonal spring that sits behind the bottom ring, drawn as a zig-zag)


ALSO, without any parts diagram/manual i don't know the ring gap clearance

and to run her in the plan was 30minute rides at half throttle then 3/4 throttle, with proper time to cool betwee runs, for about 300 km. sound reasonable? the cylinder has been bored out 0.25mm, new piston kit and little end roller bearing.


cheers for the help

[dogsnbikes]

you could see if there is a manual for yourr bike here http://www.carlsalter.com/motorcycle-manuals.asp

I'm doing a PE and the rings are the same so can go in anyway...you just have too found out what the ring gap should be just be cheaky and call your local honda workshop...

The PE piston has 2 holes at the front of the piston to help release chamber gases on the stroke so at least thats a indication of what way the piston goes in the honda may be the same?

Running in I have been told to let the engine warm up for awhile before setting off and running about 1/3 throttle for around an hour shifting through the gears with out straining the motor,but keeping in mind My engine is under full rebuild so treating it like its a new engine

[Crasherfromwayback]

...you just have too found out what the ring gap should be just be cheaky and call your local honda workshop...

The PE piston has 2 holes at the front of the piston to help release chamber gases on the stroke so at least thats a indication of what way the piston goes in the honda may be the same?

Don't need to gap 2 stroke rings mate...and the holes in the front of your piston are for lubrication of the bridge in the cyl exhaust port

[dogsnbikes]

Don't need to gap 2 stroke rings mate...

understand what your saying Mate....spend enough time on them and it will be second nature, you automatically know if they are right or wrong,

but it would help too make sure the they are within specifications for example on my bike the ring end gap should be 0.2-0.4mm and the ring free gap should be approx 6.5mm at least if its less it wont have a great seal,but I would expect new rings to measure greater than the min spec's and they do

[Crasherfromwayback]

understand what your saying Mate....spend enough time on them and it will be second nature, you automatically know if they are right or wrong,

but it would help too make sure the they are within specifications for example on my bike the ring end gap should be 0.2-0.4mm and the ring free gap should be approx 6.5mm at least if its less it wont have a great seal,but I would expect new rings to measure greater than the min spec's and they do

You don't generally gap em as the ends of them are machined to fit the locating pins (which stop the rings rotating on the piston and snagging on a port).

[motorbyclist]

cheers that's good news - might have it finished tonight

but if the gap is too small dont we risk seizure/damage when the ring heats up and closes the gap?

[Sketchy_Racer]

cheers that's good news - might have it finished tonight

but if the gap is too small dont we risk seizure/damage when the ring heats up and closes the gap?

I would certainly suggest checking the gap, if they are new rings going into an old bore, it is highly unlikely that there will be to little clearance rather than to much.

But if it is a newly bored cylinder, then it is very easy to end up with to little ring gap clearance, and in a air cooled motor like the H100 (I do love those little motors) it could end in tears if it got a bit to hot.

The design of the H100 rings means that there will be no effect on the ring positioning if you do need to oil stone them to gain more ring gap.

[Henk]

Should make no difference which one goes in which slot. They will probably have a letter etched onto one side of them, usually "N" from my ecperience. Thats the top side of the ring.

[motorbyclist]

well so much for finishing tonight - the new bloody little end bearing is too small

I would certainly suggest checking the gap, if they are new rings going into an old bore, it is highly unlikely that there will be to little clearance rather than to much.

wel i gave it a quick look and it was a decent gap, but i didn't bother to find the feeler guage to measure it

do you know what the clearance should be?

Should make no difference which one goes in which slot. They will probably have a letter etched onto one side of them, usually "N" from my ecperience. Thats the top side of the ring.

as i said earlier, there are no markings on the rings so i've installed as shown in my drawing