Will an '85 Cylinder and RHS case fit a '90 bottom end?

[madmcnish]

Hi guys,
Bought a complete '88 bike in VGC a month or so ago.
Got alot of spares in the sale too (almost enough to build a nother bike), including an '85 engine.
The '85 engine is almost complete, but the crank needs overhauled.
I bought another bike at the weekend - '88 frame & running-gear with a '90 engine.
The engine is a runner and I'm gonna use the forks too, but the rest of the bike is a bit of a shed.
Will the '85 cylinder and RHS (Clutch and water pump) engine case bolt straight onto the '90 bottom-end?
I know that later ('89 and younger) cylinders need the liner machined-down to fit earlier ('85 to '88) bottom ends, but what about the other way round?
What about the RHS engine case? - I know that the clutch basket is thinner on the '85 to '89 bikes, so I will have to fit the '85 basket to allow the '85 case to fit.
Is there anything I need to know before I give it a go?
I'm retro-fitting the '85 parts to the '90 bottom-end so that the water pump hoses don't foul the high exhaust.
Cheers in advance for any help / info.

[Roostius_Maximus]

You need a narrow clutch from 86-89 to use on that 90 shaft if you plan on running hte 85 clutch case, 84-85 is a smaller spline shaft so you would need to split the cases, which would make no sense so run the 85 complete

The cylinder will bolt on and have more crankcase volume, which may result in less botom end or throttle response

the hose comment makes no sense since you will be using the 85 jug outlet which causes the interference. Guys have run the low and high pipes on both style jugs

[madmcnish]

OK, looks as though I'm going to overhaul the '85 engine and use it.
I think I can remenber reading before that the hole in the swingarm bushings require to be machined-out to accept the '88 swingarm spindle???
Is this correct?
Roostius, If you use an earlier engine in a later frame with the low pipe, the coolant pipes will foul the exhaust.
If you use a later engine in an earlier frame with the high pipe, the coolant pipes will also foul the exhaust.
The bike I bought at the weekend is an '88 frame fitted with a '90 engine and the high exhaust pipe. The previous owner has hammered a dent into the back of the exhaust to clear the coolant pipes.
Not pretty, but it works.

[nmdesertrider]

If you use an earlier engine in a later frame with the low pipe, the coolant pipes will foul the exhaust.

What does 'foul the exhaust' mean?

[madmcnish]

The coolant pipe will hit / clash with the exhaust.

[Roostius_Maximus]

so what bushing did the guy make for the '90 engine in the 88 chassis?
The 85-88 rear engine bushings are the same size

I've seen guys run that low pipe on the rear outlet jug and back the other way too.

If you have the jug off the "90" engine, take a picture of the area arround the crank and I'll confirm what year the cases are.

If you have both engines open, theres a few things i'd chage to make it "best" for the bike
:Change the mainshaft to the newer one so the basket can be upgraded later
:use the 87-01 kicker splindle, Its got more teeth than the 84-86 ones and lets you get a longer kick at it

[nmdesertrider]

85 tranny is junk I shattered two of them in 8 months and the old clutch is garbage too. It's so grabby that you can't start the bike pulling in the clutch while in gear. I replaced the ball, pushrod and cap on the clutch... nothing helps.
Do yourself a favor and get a newer transmission and clutch.

[100hp honda]

i dont agree with the '85 being junk, any bike can be broken given the right circumastances. i had a '85 way back in the day and it never broke, i guess i didnt beat it hard enough . dont get me wrong, i like the older models but i prefer the 8/7 clutch vs the 7/6 clutch, and the pancake bearing seems to be a much improved design over the ballbearing....theres also a few other things i prefer about the newer models.

[nmdesertrider]

any bike can be broken given the right circumastances.

In other words, "don't let nmdesertrider ride your bike"