Rebuilt Super Rat Compression

[viclioce]

I stayed away from the Super Rats for awhile. Got too frustrated working on them.

Today I pulled the cylinder, piston & ring from the unit which was giving me only 85 psi on my compression gauge.

Here’s the measurements I got.

It’s a .020 piston

Piston to cylinder gap is .005
Ring gap was .012
(about 1/4” down from top of cylinder)
Ring gap .011
(With ring just above exhaust port)
Cylinder taper .002

As I stated early on, it seems everything is within clearance tolerances. Minimal taper, good piston to cylinder gap, and a little higher than best for ring gap but not unacceptable.

Any thoughts? Victor

[Stever]

Victor, I reread the whole thread (which took a while - LOL !) and here's my two cents, pulling pieces from posts by Ed, Dale and Matt. I think these are the most pertinent -

Per Ed, the compression occurs from the top of the exhaust port on up.

Per Ed and Matt, check everywhere that can leak in that top area. Perfect seal at the head gasket, cylinder studs, spark plug hole? A bit of steady low air pressure though the plug hole using the fitting from a vacuum leak down tester, and soapy water brushed on the parts might expose a bit of leakage.

Per Dale, (and I REALLY stress this one) - the cylinder should be honed. A new ring and a glazed cylinder will not give the best compression. Lots of heat happens in the compression area (which is also the ignition area), so it is almost bound to be glazed to some extent.

Just my Readers Digest Condensed version of what has already been said. Good luck!

-Stever

[viclioce]

Well, I pulled it all apart today. Some of the measurements don’t make sense. It seems to be within tolerances based on the measurements I posted. However, I think the big issue is irregular tapering of the cylinder. This is causing the piston to stick a bit.

So, I packed the cylinder, piston & ring up for shipping & im sending it to Terry tomorrow for a Hodaka Dave inspection and whatever work Dave says it needs. I’m sure it will come back from Dave ready to run, just as stuff always has. Then I can get this bike shipped to Florida!

Never again! I will not do this backwards again. First build a bike & work the bugs out. Then, once it’s running consider a buyer and not before.

I tried to short cut this Rat and it came back to bite me in the A$$!!! Never again! I let this get the better of me & then I got pissed off with it & didn’t want to work on it. I should have pulled it apart 3-4 months ago and sent it to Dave. Lesson learned! Victor

[viclioce]

Was advised by Terry that Hodaka Dave had to hone the cylinder. It should be back in the mail after they return from Vermont. Victor

[viclioce]

I tell you this bike is cursed for me.

I got the cylinder back from Terry on Monday. I put the piston on while the bottom end was still on the bike. Cylinder on, head on. Head nuts torqued.

Motor kicked over much easier now that Hodaka Dave did his magic. Kicked it several times. After about 5 kicks Brup Brup. Kick again. Brup, brup, brup. Kick again. Brup, brup, berrring-a-Ning-a.Clunk!

After all that, I knocked the top rod bearing off when mounting the piston. Didn’t see it fall into the crank. Smashed the bearing and bearing needles trapped between the piston & cylinder….

This was a fresh .020 bore and new piston.

I hate this bike…

[givergas]

!@$%!!&%@$#! fud ruker............

[taber hodaka]

You hate it, I love em, I get your headache you get my gold, fresh out of my mine. How much Gold $$?? There are simple ways to avoid what happened here, so it won't happen to you again. You are not the first one, with this problem. I hope to someday do a video of --- back yard mechanics--- [simple hodaka repair].

[Bruce Young]

Victor, don,t dis par, this has happened to lots of two stroke mech., thru the years, you are not alone, most won,t admit it happened, so you a better person for talking about it. We all have had little embarrassing things like this happen. Take a deep breath and step back and think, and then go back at it. Good luck ol friend. you will get it done.

[viclioce]

Thanks Bruce! Victor

[viclioce]

Well the cylinder went off to Terry on Monday. While I was waiting, I put the bottom end back together. However, upon installing the kick lever, even with a new spring, the kick lever was not properly returning.

So I split the cases, pulled the O-ring out from the case & found the O-ring had hardened & was binding the shaft. Luckily, I had a 1/2 dozen extra.

I replaced the O-ring with another new, but softer one & a little grease on the shaft. And it seemed to slide thru smoother. Reassembled the bottom end in about 45 minutes including torque-ing & installing covers. Just waiting for the cylinder to come back with another piston kit. Victor

[taber hodaka]

Victor INVU for all that you do, have done and that you stick with it. Some day I want to share tricks of the trade with you, tools and mechanical aids you can build for yourself. You might consider having Terry fit a wrist pin for the piston, as it should be a finger fit. I use a simple homemade engine stand with the wrist pin hole about eye height, it will rotate so you can see both sides and have good lighting. You could build it for about $20.00dollars in an hours time. you would need something that will cut metal and a electric drill. Clarence

[bobwhitman]

Clarence
How about doing an article for the Resonator Revisited on that stand? Others than Victor could use one.
Bob

[viclioce]

Clarence. My mistake was in not taking the bottom end out of the bike. I also didn’t cover the cylinder opening to the crank. 2 things I usually do when putting a piston on a rod.

Would love to see the stand! Sounds like something cool to build! Victor

[viclioce]

Today is a good day. I got the cylinder & top end kit from Terry a couple of days ago. Everything is back together and….

The Rat started up!!! Yeay! The big issue was the condition of the cylinder first go around. After honing, it began to start until “you know what” happened. Cylinder bored with a new top end kit and the top rod bearing installed properly & she runs!

Looks like I still need some minor adjusting of the throttle cable and the slide is sticking a bit, but it’s nothing I can’t work thru!

With persistence & being able to discuss things here, I was able to work it out. Thanks to all who contributed!!! But especially to Clarence who spent a lot of time on the phone with me! Victor