Problems after rebuild

[SuperRat2110]

Hey guys, I don't have any compression numbers but after replacing the seals and bearings on my Super Rat 98 it doesn't want to kickover. I can tell the compression isn't there. Where should I start? It ran before I broke it open so I'm assuming this is something I did wrong. Any suggestions or common mistakes guys make when reassembling?

[SuperRat2110]

Well after trying to do a leakdown test, I found the culprit or at least I hope it is. The Rubber flange coming of the the motor that attaches to the carb has a crack in the top of it. I didnt notice anything before so I'm assuming it happend while taking things apart. Maybe it had already started and I made it worse.

[Bill2001]

The bad carb mounting flange wouldn't have bearing on the low compression.

[SuperRat2110]

That's kind of what I was thinking also buy wasn't sure.

[SuperRat2110]

Is there a sealant that I should have used between the cases? If so could this be causing a compression issue?

[Bullfrog]

Yes, you most certainly should have used some sealant on the crankcase halves. Modern automotive anaerobic sealant is my recommendation. It is intended for just that sort of use AND it can be removed/cleaned off without an act of Congress the next time work has to be done "inside". BUT . . . not using the sealant on the cases would have NO effect on lack of compression. Once you repair the intake manifold leak situation, be sure to re-do the leak down test to assure your cases are sealing properly. In the absence of sealant, I'm worried . . .

I have to wonder about a broken ring on re-assembly. (that would have an adverse effect on compression).

Ed

[thrownchain]

Did you hone the cylinder and put in new rings? Head gasket good (new)? Proper torque to the head nuts? Piston to cyl specs in spec?

[SuperRat2110]

I put in all new gaskets. I didn't hone anything. Piston and ring looked pretty good. Dint replace anything up there. Torque is good.

[SuperRat2110]

I took the head off and checked to make sure I had it orientated correctly. The ring was in place and fine.

[Bullfrog]

Can you hook up a compression gauge and run a compression test? Throttle held wide open, kill button depressed, kick till the gauge stops rising. (Um, cylinder and Piston/ring pre-oiled on reassembly?) A bit of oil helps seal.
Ed

[SuperRat2110]

Just put it back on...I did shoot some wd40 in cylinder. It does seem to have more compression just doesn't want to turn over. Ill check compression.

[thrownchain]

Define doesn't want to turn over.

[SuperRat2110]

I can't define anything right now. Lol. Won't start! Com pressing is reading 145 now. So that is good. I feel like I have some clutch issues. When I dont have the clutch hooked up it feels like it wants to run. If I hook up the clutch it barely sputters. Sorry guys. I know this isn't helping you help me.

[SuperRat2110]

The clutch might be the problem, when I originally tried to start after rebuild I had it all assembled. Second time I didn't have it hooked up.

[SuperRat2110]

Just checked for spark and it seem like I don't have that either. So right now I really don't know what the issue is. Seems like I could have a couple things not working. Thanks for the replies, I know you're all probably rolling your eyes!

[thrownchain]

Different ideas, won't turn over to won't run. 145 lbs is good for compression. Technically if you have spark at the correct time and the right amount of fuel it should run. If there as an issue with it not spinning over correctly then the kickstarter needs attention. No spark check the point and cond, and the wiring to the coil.

[SuperRat2110]

Kick start seems to be fine. I get plenty of sputter when I do kick. It's positioned correctly. All the wires are hooked up. I believe there was 3 of them that I took apart to strip the bike down. So I guess until I get a spark that should be my objective right now.

[SuperRat2110]

Hey Guys, Good news! I checked the lawn mowers spark plug, same thing. Took over off cover and I had was screw that I know I tightened down on the rotor magneto thing? I tightened that SOB down and bang, she fired up. Thanks for hanging in there with me. My teachers always told my parents growing up that I rush through everything. Well that hasn't changed. It's just how I'm wired. Thanks again. Hopefully whatever other problems I was having aren't really problems at all.

[SuperRat2110]

The clutch is still really finicky. It doesn't really let the gears grab uptil it's almost all the way released. I have it adjusted to the point where the lever that connects to the clutch cable is almost hitting the cover. I opened the the clutch when I had it apart and all the plates where separated. Not sure how to tell if they're too worn. Maybe I should replace them all. Any suggestions.

[Hydraulic Jack]

SR2110, does the clutch function now the same as it did before you took it apart and put it back together?

Check friction discs with a caliper or micrometer to determine if they are worn. The thickness of the discs changed a bit from model to model, but the spec is listed in the supplement for the 98 Rat and on the Strictly Hodaka website. Book value for new discs for your bike is 2.5mm.

https://www.strictlyhodaka.com/v/vspfil ... /SH_98.jpg

But let's go back to your question about whether you should have used sealant between the engine cases. That's a show stopper in my book. I suppose it is possible that the cases won't leak if no sealant is used, but I simply would not go there. The problem is that while you can see transmission oil leaking along the seam if that part is leaking, you may not see much if the crankcase is leaking. Eventually you would see wetness, but my guess is that it will seize long before you see fuel leaking out the case seam because it will be sucking air. You could do a leak down test, but really, if you didn't use Yamabond or Hondabond, or some equivalent anaerobic sealant, I would not run the engine. Silicone sealant is NOT appropriate here. Not even Right Stuff. The machine work on the case seal margin is not intended for dry assembly.

I hate to mention this, but when you put the CDI back on the crankshaft (that rotor magneto thingy) did you set the timing?

[SuperRat2110]

No timing was set. I simply put it back on the way it came off. Not sure how you set timing. Clutch worked that way originally after I bought it or at least similarly. But after locking the rear brake a few times it did improve somewhat. Looks like I have some more work to do. Can you explain the timing thing and is it important now that the bike runs again.

[Hydraulic Jack]

At the risk of sounding like a killjoy, please don't ride the bike until you have secured a repair manual, and if you don't already have the tools, a compression gauge, screw in type not the rubber push in type, a rotor puller, a torque wrench that runs right and left registered in the 250 inch pound range, some Hondabond 4 or the equivalent, a dial indicator with a spark plug thread adapter, an impact screw driver (hand driven not electric), and the bits and pieces to make a leak test rig.

I know this sounds like a lot of stuff, and I suppose it is, but a dealer back in the day would have had much more at their disposal. What you face here is a complete engine strip down and reseal, and to do this safely you need some tools.

To answer your question directly, yes, you need to reset your timing even if the engine is now running. It isn't all that hard to advance the timing, and even a little advance will lead to detonation which can, in short order, burn a hole through your piston. If all this seems overly conservative, I can say with personal certainty that it isn't. But it is up to you. You have a motocross bike with a high output engine that has, so far, three identified problems any one of which can cause engine failure: 1) a leaking intake manifold; 2) an unsealed crankcase seam; and 3) unverified timing. Each of these issues is capable of leaning your engine to the point of failure, or in the case of timing advance, causing spark timing beyond the control of modern gasoline. The CDI system in the Super Combat, and I am guessing in the Super Rat also, had a tendency to advance timing at high rpm instead of backing off a bit. Back when you could actually buy 92 octane gas or better at the local gas station, it was less of an issue than it is today. These days most 92 octane fuel has ethanol which is not at all good for air cooled engines, and nowhere near as good as fuel from 1974.

I will let others comment as they will, but I personally think you should slow down, be prepared to rebuild the cases correctly while the bike is still running, and assure safe use of the engine. Otherwise you may have to do it anyway in the near future, plus rebuild the cylinder and piston and quite possibly the rod and crank as well. Up to you.

[matt glascock]

What he says. Some of this stuff is heading into the realm of the unobtanium and if you can find it, you'll pay a lot for it. Wreck that jug and then find that it is on its last overbore would be sickening. Trash the rod and crank shaft in the process and you'll need to remortgage your house for replacements. What is it Harry Taylor said? "Slow down. You'll go faster." Sage advice.

[matt glascock]

What he says. Some of this stuff is heading into the realm of the unobtanium and if you can find it, you'll pay a lot for it. Wreck that jug and then find that it is on its last overbore would be sickening. Trash the rod and crank shaft in the process and you'll need to remortgage your house for replacements. What is it Harry Taylor said? "Slow down. You'll go faster." Sage advice.

[SuperRat2110]

Ok, so I know I should break it back apart and put some sealant on the 2 halves. All the seals and bearings have been replaced. So right now double check my torque specs and seal. Possibly look into clutch rebuild. Hard to do a leak down right now because all the air going in goes straight out the carb flange. I have a homemade tester that works good. So when I get some of these parts ordered I will do what I should have done. I plead ignorance because this is a first. Maybe it was a given to put the sealant on but again, ignorant to that. Once I get that done. I'll look into timing and leakdown. I'll have to get a manual also. Thanks for the tips I appreciate it.