Reinstalling engine on RD400C

[Membername]

So the engine has been on the bench for a year, do I just fill it up with gear oil and good to go or should I do some sort of rinse first?  I didn't split the cases.

Thanks,
Karen

[Yamaha 179]

Karen:
Did you pull the right side cover off, remove the clutch assembly, check and clean those parts?  Did you change the cover gasket, etc?
If you didn't pull the side cover and only pulled the engine and put it on the shelf to do chassis work/clean up I see no reason to flush the engine with mineral spirits.
Lyn Garland

[motodreams]

Reinstall and run unless you have a good reason to do otherwise.  Could put a touch of 2-stroke oil in cylinders if you wish as likely totally dry but its a give er and go situation   clutch plates may be a bit sticky at first.

[Membername]

Lyn,
I did pull the side cover and cleaned/checked the clutch plates and springs. And I have a new gasket for when I put the cover back on.  In this case should I do a mineral spirits flush?  The bike hasn't been started since 1989.

K

[motodreams]

Not necessary at all unless you have reason to think there are contaminants inside engine in which case likely a bigger problem exists...

[Yamaha 179]

Karen:
No need for flushing the transmission.  I do recommend you use an oil specifically for motorcycle transmissions.  I use Pro-Honda trans-
mission oil SAE80W/85W oil in our race bikes with six ounces of gear oil enhancer.  (The enhancer was recommended by R&D Motorsports, THE transmission shop for folks like us.)  You do not want to use common engine oil as it can cause problems with your clutch plates.  I use the Honda oil in our road racers because it is less expensive than the other oils and we change it frequently.  I have never had gear box problems since starting with this process even though the bikes get worked pretty hard.
Lyn Garland

[Membername]

Thanks Lyn, I've already purchased Bel-Ray 80W Gearsaver transmission oil.  I'll look into the gear oil enhancer.

K

[Yamaha 179]

Karen:
The gear oil enhancer is really unnecessary for a street bike; they just don't get used that hard.  But, what I use is MGC, Multi-Gear
Concentrate, Part Number 325, from BG Products, Inc, Wichita, KS, www.bgprod.com.  Comes in a six ounce bottle.  I couldn't find it in a local parts store and had to contact the company for a source.  Good stuff.
Lyn

[quocle603]

You should do a leak down test since it's out. Eliminate those airleaks that you might have.

[Membername]

Yep did the leak down test, pumped it up to 6 and it held at 5.5 for 6 minutes.  There is a really, really small leak at the base gasket.  Should I worry about this tiny leak?

K

[Organicjedi]

I wouldn't want any air leaks there. They only get worse until they cause you to blow up. Changing the gaskets is much easier with the engine on a bench too.

Changing the gaskets will also let you look at the health of the top end. Do both sides. It's extra work but you'll regret not doing it if you blow up. 

[Membername]

Top end has already been apart and inspected.  I used a new base gasket, but it was from yambits.  I'll try re-torquing the heads and if it still leaks I will get oem.  Do you put anything on the head bolts?

K.

[SUPERTUNE]

What torque spec did you use?
I think the oem manual says 17 ft-lbs, but on 400's I have found that too low!
I use 23-24 ft-lbs and 25 ft-lbs on race bikes.
Not 350's though unless you mill the cylinders for the 400 gasket conversion.
I use only 18 ft-lbs on ring gaskets, any more just makes the heads warp and leak worse.

Chuck

[Membername]

Torqued the heads to 24 ft-lbs and I didn't see any leaks.  It lost only 0.5 psi over 10 minutes so it should be ok.

K

[SUPERTUNE]

Torqued the heads to 24 ft-lbs and I didn't see any leaks.  It lost only 0.5 psi over 10 minutes so it should be ok.

K

Your good to go now...
Retorque after a couple heat cycles, do it at room temp.
C