250SX, Gotta question......

[the great gazoo]

I've got an '85, which has a bad transmission, & I recently aquired an '86 that smokes- the plan is to put the '85 top end on the '86 bottom. Now, the reason I'm asking,and I did search this forum, is that when I was looking gasket sets on fleaBay, a couple of them are listed as '86-'87 SX kits.
Am I good for this swap?

[dustrunner]

if it smokes but runs good i would just put new valve seals in the 86 engine and possibly new rings after looking at the piston and cylinder.. but thats me...

[dougspcs]

Agreed a top end refresh is easy if you are going to have it apart anyway..hone the cylinder and fresh rings you're done.

I don't think the 85 top end is a direct fit..chain guide differences if I am not mistaken.

The only PITA is the fact that the engine needs to come out to work on the top end..that was one thing I did like about the Yamaha's!! Rering them in the bike and away you go..

[the great gazoo]

I kinda figured I'd haveta go that route, so I'll get it appart & mic the cyl, see what's up & get rigs & a hone job, thanks & sorry it took me a while to respond, 12 hr day at work..........

[dougspcs]

While you're at it, hearsay is that the 85 has a less than perfect cam chain and guides..double check with the others but it would be a good idea to cover that ground while you're at it!!

Then you'll be able to rock the next 25 years.

[the great gazoo]

Thanks, Doug. I'll check into that as well!

[Howdy]

Agreed a top end refresh is easy if you are going to have it apart anyway..hone the cylinder and fresh rings you're done.

I don't think the 85 top end is a direct fit..chain guide differences if I am not mistaken.

The only PITA is the fact that the engine needs to come out to work on the top end..that was one thing I did like about the Yamaha's!! Rering them in the bike and away you go..

Doug, I have done a couple top end rebuilds without pulling the motor. I removed the cylinder studs ( using the 2 nut method ).

Remove the head top cap.
Remove the main 4 studs.
Once the studs are removed the head and cylinder will come right off.
Install in reverse order. Put a drop of blue loc-tite on the studs when putting them back in will keep them in place. I learned this from a Honda Dealer many years ago when I watched them pull a top end off a 250es. They used a special stud puller though ( 2 nuts are a lot cheaper. LOL ).

You might have to remove / loosen the low engine mounts, but it still easier than pulling the heavy motor. ;)
Howdy

[dougspcs]

Excellent work around Howdy, I'll remember that in case the need arises!!

I just learned the trick to pulling the engine on a ES/SX and putting it back..it's not as bad as I thought.

But still it's good to know the options are there..

[honda4h]

i have swapped out top ends 85 to 86 i didn't see anything different and motor worked fine it's a cheaper way to go. just need new gaskets. i did that 6 years ago i had the same thing bad trans on one motor but ran a1 the other smoked but good trans. as recommended new timing chain. id even change the one way bearing id bet it going. buy it pricey