Hello, all.

As mentioned in the new member introductions, I recently acquired a 1973 RT360 that has not run for years, but was stored indoors and is pretty decent shape.

Upon unloading the bike at my shop, I pulled a plug and tested for spark and was pleased to find that there was s decent, but not great spark.  I then tested for compression and found I had about 60# so I tore down the top end to take a look.  

The piston had the usual accumulation of carbon on the dome but the skirts and cylinder bore looked pretty good.  However, once I measured everything up, it looks like it's ready to go tot he first overbore.

I also inspected the connecting rod fit to the crankshaft and found that there was more play than I like to see,

It looks like it's time to go ahead and tear it down to replace the bearings and seals.

Do you guys have a preferred vendor who can supply most of the parts I will need to take this on?  My shopping list, so far, is as follows:

• Overbore Piston & Rings
• New Coil
• New Points
• New Condensor
• Engine rebuild kit (seals &   gaskets)
• Connecting rod and wristpin bearings
• Possibly all bottom end bearings

Any and all advice would be gladly welcomed.

Thanks!

-VDP

This are not the only options just a few I thought of.  See if that helps.   BTW, I would check that decompression valve first before going all out on the engine. 
Enduronut.
www.legends-yamaha-enduros.com 
Seach the forum, his info will come up. He has a supply of the best piston/ring combos. 

amazon for EMGO coil; I have 2 both worked. lots of aftermarket, DO NOT. 
KDI Repro for points
ebay condenser (I forgot who I used though); better make sure that ones compatible.
bearings.  partzilla, yamaha, ebay, but always OEM if possible. this will LIKELY eliminate the need for new shims on crank, drive axle, main axle, etc.
gaskets: D's Unusual Finds Gaskets
seals: if d's doesn't have this, I would use brand name
seals: D's Unusual Finds

Thanks, pabdt.

I did check Legends Yamaha Enduros before I posted, but they did not have the rings or pistons for my machine.  However, I was able to look up the factory part numbers and find NOS replacement on eBay which I have already ordered.

With respect to the ignition parts, I have used Emgo parts on several other bikes with good success, so I will order a replacement from them as well as points and a condenser from your suggested vendor.

As I dug deeper into the parts manuals, I was able to locate the generic bearing numbers but your recommendation to use OEM did not go unnoticed, so before I assume that all the bearings need to be replaced, I will first tear down the engine to ensure that they are truly needed.  Apart from the big and small-end rod bearings, I have no reason to suspect that the rest of the bearings are bad.  The machine only has around 4K miles on it, so the bearings should not be work out.  My only cause for concern is the issue with rust forming on them as two-strokes don’t carry oil in the cases the way a four-stroke engine would.  If the bearings check out then I don’t see any need to replace them.  Fingers crossed!

I have gone ahead and ordered the seals and gaskets from “D,” so by the time they get here I should have the engine taken down, all the parts cleaned, and the cylinder bored so it should only be a matter of putting her back together.

Finally, I did inspect the decompression valve and found that it was faulty, but I will introduce that matter in a separate message in an attempt to maintain focus on this thread.

Thanks again!

-VDP

All-

With regard to pabdt's comment about checking the “decompression valve first before going all out on the engine,” I did do that and found that the cable and spring were missing, so when I checked the compression, I might not have gotten a good reading.  However, when I measured the bore, I found that there was enough wear to warrant an overbore, so because I was above the acceptable wear limits, I have decided to definitely rebore the cylinder, but while I'm waiting for the parts to come in, I will also go ahead and replace the spring in the decompression valve, reassemble the top end, and remeasure the compression.   

The thought behind that is that if I can get it running and perform some limited tests on it I should be able to determine if the gearbox is in good order and see if there are any other bits I need to order before the full teardown.

The carburetor, as expected, was a “bit” gummed up, so I’ve already taken it down, cleaned it up, and ordered an overhaul kit for it.  I have already de-coked the piston and head and cleaned them up, so they are ready to go back in.  I have also deglazed the cylinder and re-honed it just to give the old rings an opportunity to seat once I reassemble it.  

One thing that I did find while I was inspecting the bottom end was that the Yamalube oil pump starter plate was not connected to the pump and simply fell to the floor as soon as I removed the cover. This leads to my next question which has to do with removing the pump from the system entirely.

I understand that this system could be considered a convenience, but I am also confident in my ability to be able to pre-mix the two-stroke oil with the petrol and not risk a seizure if the pump fails.  I see that rebuild kits are available and plenty has been published on how to undertake the rebuild, so what’s the common wisdom on this?  Do I maintain the original system, or blank it off and simply premix the oil.  If I do premix the oil, what’s the recommended ratio?  50:1?

Thanks,

-VDP