Stuck ring?

[paul1478]

76 RD400. Stage 2 Chuck build. Forged Wiseco pistons. 
My bike had been down on power for a while.
I have an appt with DR Quinzler on the 6th to swap pistons in hopes of fixing the issue.
I noticed when I took the top end off only the upper ring was free. I see a bottom one but it is stuck tight to the piston. Bolts sides. This cannot be right can it?
I also noticed what looks to be oil on the crank does not look like 2 stroke oil.
It has been sitting for months.

[m in sc]

i mean.. it could be trans oil but? doubt it in both.

no, the ring should be able to move . say hi to chuck. 

[paul1478]

i mean.. it could be trans oil but? doubt it in both.

no, the ring should be able to move . say hi to chuck. 

Thanks Marc I hope it is a stuck ring because that would answer a lot of questions. Also good to know it's probably not trans fluid thanks as always for your words of wisdom and I will absolutely say hello to Chuck and see you next month.

[m in sc]

last build i went with woessners. I never liked wisecos. good luck w it.

[RDnuTZ]

i mean.. it could be trans oil but? doubt it in both.

no, the ring should be able to move . say hi to chuck. 

Thanks Marc I hope it is a stuck ring because that would answer a lot of questions. Also good to know it's probably not trans fluid thanks as always for your words of wisdom and I will absolutely say hello to Chuck and see you next month.

you mentioned it being down on power? If you weren't able to get into upper rev range to clean it out there could be residual 2 stroke oil residue left on crank- maybe that is what you are seeing after it sat for a while? Didn't mention if you are premixing or not and what 2T oil running, but if lower end was really heating up it could certainly discolor your oil residue like that.

[RDnuTZ]

i mean.. it could be trans oil but? doubt it in both.

no, the ring should be able to move . say hi to chuck. 

slight side tangent on stuck rings: I haven't rebuilt an RD top end in many years but remember there used to be a lot of discussion around the ring expanders that came with some RD350 piston kits. Some people said use 'em and some said toss 'em. Was there ring expanders application for RD400 as well?

[paul1478]

you mentioned it being down on power? If you weren't able to get into upper rev range to clean it out there could be residual 2 stroke oil residue left on crank- maybe that is what you are seeing after it sat for a while? Didn't mention if you are premixing or not and what 2T oil running, but if lower end was really heating up it could certainly discolor your oil residue like that.
[/quote]
The bike would rev clean all the way to 9000. New it was 64hp on the dyno. Felt more like 50. Ran ok. Just not what it was. Plugs perfect color.
Chuck moved the timing jets changed pipes. I thought maybe it's me. 5 seconds on Chuck's bike nope. Bike is down on power. It was originally very close to his in power.
Yes premix only. This ring seems to make sense causing some blow by.
I'll find out next weekend.

[m in sc]

wisecos dont use an expander. just fyi.

[Vincenthdfan]

Whats the theories regarding expanders, my 350's still on original top end with expanders is why I ask...

[m in sc]

they will break over time sometimes and little bits of it can be under the bottom ring floating around. usually if the bike has been modified (higher revs, etc) it shows up quicker. I've pulled them intact out of high mileage top ends, and pulled broken ones out of low mileage top ends.

[Vincenthdfan]

Makes sense, thanks. 

[paul1478]

my motor has been re- super tuned. I spent Friday and Saturday with Chuck.
It is back to what it was plus some more. New port map, new pistons, and some jetting. Plus fixed a bunch of little items I overlooked in the past.

Ordered tires, shocks and some small items to get ready for the gap this year.
Great to have the motor back running great again.

Thanks as always to Chuck. Great mechanic and great friend.

[Kawtriplefreak]

Chuck is the man   Glad you got it sorted.

[m in sc]

so.. was it too lean, heated up and stuck the ring? what was the cause?

[automan]

Expanders are for piston slap.
cliff