Fixing up new '85 250sx

[beastybaconman]

Just picked up a pretty decent shape '85 250sx today. For the most part it's mint but there are a couple things that need fixing.

1. The reverse lever doesn't work properly. It seemed like the cable was stuck pulling tension on the reverse lockout thing so you can just shift down into reverse without pushing the button and pulling the left brake lever. I took a look at it and the cable seems free but the little lever on the right side engine case (in the first pic) seems to not have any kind of return spring. Is the spring for that inside the case?

2. There's a missing bolt on the front left of the valve cover (second pic) and it looks like the valve cover is leaking oil a little bit, maybe because of the bolt or maybe needs a gasket. Looking at a parts diagram it looks like there are a bunch of different length bolts in the head and it doesn't really show which one goes where. Anyone know what size bolt I need for that?

3. In the third pic it looks like there's a case bolt missing down under the reverse lever thing on the right case cover. Anyone know what size that bolt is?

There's a couple other things that need fixing too but these are just what I'm starting with, any help would be appreciated!

[wonderboy]

With regard to you missing cylinder head bolt, I agree, Honda didn't do as nice of a job as usual on the part diagram showing where to bolts go. Based on the pattern they are arranged in though, I'm pretty sure it is bolt #34 that you need. It is an M6 x 35. (35mm long)

Sorry but my SX is in storage, otherwise I'd go pull it out and tell you for 100% sure which it is.

[beastybaconman]

With regard to you missing cylinder head bolt, I agree, Honda didn't do as nice of a job as usual on the part diagram showing where to bolts go. Based on the pattern they are arranged in though, I'm pretty sure it is bolt #34 that you need. It is an M6 x 35. (35mm long)

Sorry but my SX is in storage, otherwise I'd go pull it out and tell you for 100% sure which it is.

Thanks I’ll try sticking some rod or something down the hole and see how deep it is, that’ll probably tell me about what size bolt I need.

Then I think I figured out the missing bolt in the right case cover. Looking at the parts diagram there is supposed to be a little cover for the two wires that go into the case right there. It’s held in by a bolt right about where that ones missing and I’m also missing the wire cover so I’m guessing that’s my problem.




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[beastybaconman]

Well I got my bolts figured out and I pulled the side cover off and found my reverse arm spring was just not put on right. I also found a new bigger problem.

It doesn’t have a kick start so while I had the case off for the reverse thing I took a look to see what it’s gonna take to put a new kick start in. I found that I need all the parts for the kick start and possibly a new engine case... In the pic all that brownish stuff is JB well covering a nice big hole in the case and on the right there’s another little hole. The JB weld looks to be doing a pretty decent job so I think I’m just gonna try to run it for a while, but what do you guys think about that hole on the right? Should I try to patch that somehow or will the kickstart still function ok with that hole there?


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[beastybaconman]

Just got a new set of case halves ordered. I’m having a hard time finding a bottom end bearing kit though. Anyone know where I can get one?


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[beastybaconman]

Well looks like there isn’t really a bearing kit for these so I’ll just check them all and replace any that are bad. I’m definitely going to replace the crank bearings either way, but again the parts diagrams are confusing me. So in my manual it shows that there’s 1 right and 1 left crank bearing but in the diagram on the parts website it shows 2 bearings for the right side and they have different part numbers. Anyone know what the difference is? Did they just use different bearings for different year 250sx’s or something?


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[wonderboy]

Bearing #17 is your left bearing.

I don't know from personal experience, but looking at that crankshaft, it seems that the right side is pretty long. My guess is that bearing #18 is the one that goes right up close next to the crank throw and then bearing #20 supports the end of the crank further out away from the throws towards the primary reduction.

EDIT: That doesn't seem likely the more I think about it... I really don't know which of those two bearings are the one you need. It will be interesting once you get the cases split what markings are on the one in there.

[beastybaconman]

Bearing #17 is your left bearing.

I don't know from personal experience, but looking at that crankshaft, it seems that the right side is pretty long. My guess is that bearing #18 is the one that goes right up close next to the crank throw and then bearing #20 supports the end of the crank further out away from the throws towards the primary reduction.

EDIT: That doesn't seem likely the more I think about it... I really don't know which of those two bearings are the one you need. It will be interesting once you get the cases split what markings are on the one in there.

Yeah I guess the only way to know for sure is check the bearings that I pull out. I should be able to sometime in the next couple days, I got the engine pulled out last night and I’m probably gonna start tearing her down today


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[wonderboy]

Take lots of pictures, use lots of Ziploc bags for sub-assemblies, and make sure to download and read (and re-read) the manual.

[beastybaconman]

Take lots of pictures, use lots of Ziploc bags for sub-assemblies, and make sure to download and read (and re-read) the manual.

That’s the plan! I’m an aircraft mechanic so that’s how I always do things anyway haha. The main thing I’m worried about is making sure the transmission is put back together right cause I’ve never messed with one. In the manual it doesn’t look too hard though. I’ll post pics on here as I go along too


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[beastybaconman]

Made a little progress on it. Got the valve cover off and cam out but couldn’t get the Allen head head bolts off so I just pulled the head and cylinder off as a unit. Started pulling stuff off of the right side and something weird happened, when I went to pull off the centrifugal clutch the nut for it was only hand tight. Then in the manual it says to use a puller to get the centrifugal clutch off but I just slipped it off by hand. Not sure what’s going on there, probably just wasn’t put on correctly. Then I took a look at the oil screen in the bottom of the right side and I found a random o-ring chilling on it, along with some pieces of metal. Hopefully it’s just pieces of the case from the holes and not any of the internals. That’s about as far as I got tonight since I didn’t have the right wrench to pull the manual clutch off.

I have 2 questions though: What’s a good way to keep the manual clutch from spinning while I take the nut off? And does anyone have any tips for getting the Allen head head bolts out? The head bolts are kinda stripped out and wicked tight




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[wonderboy]

Nice progress! Funny now that you mentioned that you were an A&P, I was paying more attention in the pics and noticed a nose strut in one of the pics. COOL! (I'm a private pilot).

For the manual clutch, be careful how you proceed. The official way is to use a clutch holding tool. I made one. It will be a piece of steel with 4 holes in it to bolt to the pressure plate (after removing the hub and springs that are there now). On the piece of steel, weld a long handle. In the middle, you need to have a hold to allow access to the center nut. (Lets see if this works: https://encrypted-tbn0.gstatic.com/i...w8JxOFv7Zt0YQM)

Read the manual to see if it is left-handed or right-handed thread on the nut (don't remember and don't have the manual files with me at work)

I've tried this job before just wedging a screwdriver in between those 4 bosses and broke the boss off, so DON'T DO IT! You'll need to share the load across all 4.

A quick possible way though is to just try an air impact. There is probably enough inertia in the manual clutch to remove the nut. However, on reassembly, you'll need the tool anyway in order to be able to properly torque the nut

[350for350]

I have used an air impact to remove these nuts before. It's almost like cheating, but not quite. I have also broken the boss off. Not a good feeling!

[beastybaconman]

Wonderboy that’s pretty cool you’re a pilot! If you ever fly into Burlington VT then you’ve probably dealt with the FBO I work at haha.

Thanks for the tips for the clutch. What I ended up doing was using some washers on the clutch bolts so the spring tension was holding the inside from spinning. Then I just jammed the gears with a rag to keep the outside part from spinning and used an impact and the nut came right off. I’ll probably try building or buying a holder tool to put it back together so I can torque it right. After the manual clutch was off I pulled everything else off the right side and started on the left. When I pulled my starter reduction gears out it looks like one of the gears (gear C according to the manual) was blued like maybe it overheated at some point. Anyone have an idea what might have caused that?

Then I got my left cover off and pulled out the gear shift mechanism and the flywheel bolt. I’m kinda stuck here for now though since I can’t get the flywheel off. In the manual it shows a puller which basically just threads in and pushes the shaft out of the flywheel, is there any other way to get it off or should I just buy a puller? If I buy the flywheel puller I might just buy the clutch holder with it too.




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[wonderboy]

The puller works just as you described, a threaded "Bolt" is screwed into the flywheel and pushes on the end of the crank.

I can't remember which engine, and which front axle bolt, but there was a machine where the front axle bolt has the correct thread to thread into the flywheel and push it off. It's worth a shot to check on yours. Be sure to grease the threads.

Oh and the pilot thing, it was just a hobby (didn't do it for a living) and it's been a long time since I went up... but it's always been something I loved doing and hope to again once life lets me.