NC30 Lower Engine Mount Seized

[Le_Blur]

Hey guys, I'm in the middle of a rebuild. I recently bought a replacement engine as my existing one has a really whiney first gear and I wanted to rebuild it, so I bought a replacement as a stop gap so I wasn't off the road for too long.

I've taken all ancilleries off of the engine, unbolted the radiators, carbs, exhaust, front sprocket, etc. I'm basically left with a swingarm, frame, forks and engine. All the other bolts have undone with no problems. The lower engine bolt, however, has been a right troublemaker. So far, I've undone the locknut with the special Honda castellated socket Rick O sells, and undone the M12 (?) nut from the left hand side. All attempts to undo the bolt that goes through the frame and engine, and the slotted M20ish bolt that surrounds it, have been futile.

We started by soaking the whole lot in GT-85 and then trying to turn it with a 6mm allen key. That quickly rounded off. So then we knocked a T40 torx bit into the head and tried turning that with a socket. That didn't round off, but we did manage to twist the splines on the torx bit. Either way, the bike still laughed at me. Next we broke out the paint stripping gun and tickled the bolt at around 500 degrees C. Still nothing. More heat and then a bit of persuasion with a punch and a hammer from the other end. Still nothing. I'm starting to run out of ideas.

We thought about possibly trying a blow torch, and another friend suggested the possibility of using two nuts on the left hand end and undoing it like you would an exhaust stud. I've already bought a replacement bolt, so it's really just a case of getting the existing one out by any means neccessary. Obviously, I'm concerned about writing the frame or engine off, which is why I'm wary about using a blow torch.

Has anybody come across this before? Any ingeniously little tips that makes this all a doddle? Or should I just use a bigger hammer?

[vfrman]

This may sound stupid, but if all the other engine bolts are removed, do you have the engine sitting on something so there is no weight on this last bolt?

After you take the nut off the left side the bolt should slide out. The castle nut on the right side and "slotted M20ish bolt" are nothing more than adjustable shims for the engine to frame fitment.

I have never had a problem with these bolts coming out (done it at least four times now).

[Drunkn Munky]

IIRC the bolt/spindle your on about just slides out once you have removed the nut from the left hand side of the bike, if its as stif as you say then something isnt right. The 6mm allen key fitting on the bolt is just used to turn the adjuster bolt in and out. I havent removed a NC30/5 engine for a while but have done countless ones in the past and im certain thats how its done, its certainly done that way on the NC29 engine i fitted recently.

[Le_Blur]

This may sound stupid, but if all the other engine bolts are removed, do you have the engine sitting on something so there is no weight on this last bolt?

Oh, I forgot to mention that we have the engine supported with a trolley jack and protective plank of wood under the sump. I'm pretty sure there's no weight on the bolt. After realising that the bolt wasn't going to just slide out like everybody says it should, we replaced the other engine bolts to help unload any weight on the seized lower bolt.

I honestly can't see what we've missed. I'm working with an ex-Honda technician so I'm pretty sure he would've stopped me if I was doing something idiotic.

[vfrman]

In that case, I am baffled as well. Can you take some pics of both ends of the bolt? I would like to say have a go at it with a huge drift and hammer, but like you said, I can't see what you've missed...

[Dgeoff33]

I've had a couple of those seized before, if you hit it too hard it ends up breaking the alloy round the bolt.

I tried loads of penetrating oil and then some heat, neither worked!!

[pauliealdridge69]

I've had a couple of those seized before, if you hit it too hard it ends up breaking the alloy round the bolt.

I tried loads of penetrating oil and then some heat, neither worked!!

You still got some frames for sale Geoff??
I feel one could have a home soon....

[Dgeoff33]

Yep, still have a few.

[Le_Blur]

You still got some frames for sale Geoff??
I feel one could have a home soon....

Oh, don't say that...

[Le_Blur]

Muhahahahahaha! VICTORY IS MINE! BOW BEFORE ME NC30, FOR I AM THE MASTER OF SEIZED ENGINE BOLTS!

Sorry, I had to get that out. I'll keep it in my head next time. Needless to say, the little monkey gave up and saw things our way. Apparently, if you tighten the bolt back up and pivot the engine around it, it does wonders for unseizing seized things. So there you have it. Let the re-build commence.