1979 RM80N Roach

[alexbrown64]

OK, i fixed the front brake squeak.  It was the brake springs rubbing on the inner hub.  The drum brake springs are bigger than the OEM ones and just touch the hub, so i reused the old ones, which i had zinc plated a long time ago and had kept as spares.  All good.
A big problem though is the rattle i heard and mentioned in a former post.  Nothing loose... but i have a bad case of pinging.  Sounds like a can of loose bolts in there.  I had the last size overbore and it has played havoc.  I opened up the top end and the head gasket protrudes into the bore.  I modified it to suit the bore.  However, the head will need machining.  The squish, diameter and everything is all over the place and will need to be matched up to the bigger bore.  Anybody know someone in Perth who does a good job. 
Once that is done, the boy should have a great bike, as that was the only two problems.
Cheers,
Alex

[reg]

Hi Alex, great job , how did the spokes go ?

[micko]

Alex,
I use Ray Easson motorcycle engineering in Bayswater, been around a long time and knows his stuff.
cheers

[Richo52]

Hi Alex I have finally got hold of a an RM 80C to fix up.It has the later X motor but that doesn't bother me as it looks the same as the C motor.Would you have the serial numbers for the frames.I tried the US site but it doesn't correspond with our aussie models.Its taken me 10 years to get hold of one of these so Im pretty happy thanks to my mate John.Cheers Richo.

[alexbrown64]

Reg, the spokes were great.  Fitted well, looked good and had no problems and the price is great.  Micko, cheers, i did give him a ring but a bit pricey.  I sent the head to Ian Williams in Adelaide.  Have not got it back yet but will report on progress.
Nice work Richo, the C is a great bike.  I hope the B and N rebuilds help you out with your bike.  Rod at http://www.radmotorcycleshockyrepairs.com.au/ can rebuild those old shocks and the Rolls Royce paint is a great match.  My B has a frame number 12447 manufactured on 11/76.  My N frame number is 47830.  The C on http://www.vintagefactory.com/1978_suzuki_rm80c.htm is about the nicest example i have seen.  Good luck with it and hope you post up some pics.

[Richo52]

Hi Alex not sure how to post pics mate ......any pointers would be appreciated.Cheers.

[alexbrown64]

Easy Richo, just register with www.photobucket.com and upload your pics to them.  For each pic, they give you a link, which you cut and paste into this forum.  Its free and easy.
Cheers,

[oldmxracer]

The RM looks like a perfect fit for the lad. awesome awesome awesome!!!

[alexbrown64]

Its been a while and the little N' has been in bits waiting... I got the cylinder head back from Ian Williams tuning in Adelaide after he had to make a jig and machine the head to match the cylinder.  I refitted it still using the two base gaskets.  I know this will alter the port timing a bit but i want to make sure i don't get the pinging back.  Everything was torqued down to spec ready for the next step......


I made a leakdown tester for about $15 using a cheap 10 PSI gauge from Ebay and fittings from Bunnings.  After fixing leaks in the leakdown tester, spark plug hole and exhaust manifold, i was ready to do the test.  I pressurized the engine to 6 psi for 5 minutes and it held perfectly.  So, in theory, my main seals should be OK and manifolds, head gaskets etc.. not sucking air.


I purchased a new needle and pilot jet from MikuniOz and fitted them up.  I am hoping that all these minor changes and mods will eliminate the pinging and settle the idling down.  I hope to get it back together for a test in the next few days.  I may still go with a new ignition as the original is looking a bit old and turning the stator from side to side does not seem to have an affect on rpm... looking at an HPI ignition... http://www.hpi.be/item.php?item=068K338

[alexbrown64]

OK, got a brand new Mikuni carb from MikuniOz and i jetted it exactly to OEM specs using new needle jet, jet needle and pilot.  Put the bike back together and it started 4th or 5th kick.  I let the old girl warm up and i still cant get the idling to settle properly.  In fact, when the bike is on the stand idling, it will idle slightly high for 5 or 6 seconds, then idle a bit lower for a while, then idle a bit higher again.  Any idea what that usually means?  I took her for a spin in the garden and she seems to run great.... however i am still getting some pinging.  I am planning on getting the boy to give it a darn good thrashing, as since the rebuild he has only run it in and kind of blubbered around.  I think it needs Richo on it!! 
I am still contemplating putting on a new HPI ignition as i think the old one may not be perfect, and at least i can eliminate another cause.  Otherwise, it will just be a case of ride it, have fun and don't be so  pedantic.

[tony27]

Maybe try the next size up pilot jet, the symptoms you describe would normally indicate a lean condition & you've eliminated most sources of air leaks. You could also try spraying around the carb while it's running to see if the carb to manifold joint has a leak that the tester doesn't show, the revs dropping will show that something isn't quite sealed like the clamp needs to be slightly tighter

[alexbrown64]

Thanks tony, i may put the larger pilot back in that the new Mikuni came with.  I did spray "start ya bastard" around the stator side seal, carb joints etc.. but there was no change.  I will let the lad ride it some more and report back.
Cheers,

[alexbrown64]

Well, the N project has been sitting on the sidelines for a while.  Every now and then i tinker, but i get dejected when it wont run right.  I put a new HPI ignition on, and it turned into a rocket, but the top end still rattled like hell.
 
My boy wanted to ride, so he has a JR80 suzuki now, which still uses a detuned version of the 77 RM80B 5 speed engine.

I now have another cylinder and head to try and i have also purchased a 78 "C" full exhaust system.  I scored an expansion chamber, muffler, all brackets and springs etc.. from the U.S.  Very rare and should help make the N go and sound like it should.
The B and C shared the same muffler.  They used to call it a stinger and it made the bike sound like a Bee.  The N mufflers were a bit longer, a bit quieter and in my opinion never sounded as good.
The B, C and N pipes were virtually identical, except my research has shown that the N pipe had an inner perforated core to bring the noise levels down, as well as a slightly redesigned rear mount.  The B and C were brutally loud and to me as a kid sounded fantastic. I will replace the existing pipe and DG muffler with the C system.
I am determined to get the old girl running correctly.  It will just require some persistance!!

Cheers,

[smed]

  I put a new HPI ignition on, and it turned into a rocket

   

So happy with the performance of the HPI obviously , Was it the complete kit? & how do you rate it compared to the PVL on your 125?

[alexbrown64]

The first time i ran the little rm with the hpi, it made a remarkable difference.  But, the bike was still pinging.  So i left it for 6 months.  Next time i started it, it was missing.  Could be old fuel, crap in carb, dirty plug etc..  I cant really compare hpi to pvl.  PVL seems better quality but is much more expensive.  Both seem to be really good.  I am still having issues with both the yellow YZ and RM, but am sorting through them.  The HPI was good value for money and made a huge difference to the stock RM one.  The biggest difference to the YZ was the cone pipe made by Jemco.  I can swap the pipe between my yellow and white YZ and it completely changes power. Turns the 125 from a broader power band into a sharp, short and snappier power band, which i like on a 125... just keep it on the boil...

I have a lot of work commitments, but i have a new ProX piston kit for the 125 which i am giving to Ray Easson in Perth to match up.  I will also jet the bike a little richer so hopefully i get rid of the nipping up problems.
I also have a cylinder and head from a JR80 which are identical to the RM80 parts externally.  I have not looked yet, but i suspect the ports will be different.  The cylinder is still on its first size, so i also taking that to Ray Easson to match up and fit a new piston kit.  I also have the new pipe and muffler coming from a 78 model rm which was more free flowing.  So, hopefully with all these mods on the two bikes, i  will be able to get them both running they way they should, and me and the boy can go out and enjoy some VMX.

Cheers,