850 Head Removal

First time I've taken the head off and seems simple until I got to the stud at the rear of the engine where the carbs are. How does anyone get this out? Can't get a wrench on it and a socket would seem hopeless since I can't see how you get a ratchet in there . I think if I were to grind down a wrench it might be to weak to work?

I use an open end 13mm that I ground enough of the thickness off of to be able to get it around that nut

using it takes patience as can only turn the nut a little at a time

been in my tool box since 1975 and used only for that purpose

1st, get the correct Whitworth wrench, then thin out the ring end O.D. on a grinder.

concours said:

1st, get the correct Whitworth wrench, then thin out the ring end O.D. on a grinder.

Click to expand...

This is the only Whitworth wrench I have or need. 1/4w for just this purpose. But before that, I also ground a wrench to fit.

Thanks. I assumed that I would have to grind a wrench down to fit and that it would be a flat at a time.

I just pulled my head off, sent it out and for a little work so the whole process is very fresh in my mind.

I have a set of Rolson wrenches stk #46599 that I think I paid $40 for on eBay and I did have to grind the OD a little to make it fit on my 73 850 Commando.

The next hurdle you will hit will be getting the head off. A trick I learned on one of the sites (it was probably here) is to use zip ties around the intake and exhaust push rods on both sides and pull the zip tie towards the side so that it extends out to the side. Makes it easier to keep the push rods up into the head. Otherwise it it a real hassle to get the head off.

To put the head back on I use a rubber band on each push rod. I hold the head in my lap combustion chamber up, put assy lube in the sockets on the push rods, slip them on the rocker arm balls and put a rubber band around each push rod and stretch it over the exhaust rocker cover stud. The after I put the head on you can hold the rubber band, I cut it and pull it out. The push rods will fall into position. Then carefully with a pick or dental tool make sure that the rocker arm ball is in the push rod socket.

I was looking at my Haynes manual and they suggested putting bolt #1 in and after the push rods are lined up and begin tightening, just to take up the slack and keep the push rods in place not to tighten. Then follow up with the 4 bolts (#3, 4, 5 & 6). After you pull up the slack just a little you can turn the engine over and make sure all the rocker arms are operating the valves. Them assemble the rest of the nuts (2, 7, and 8) and the remaining two bolts 9 & 10. The washer on 9 & 10 are a little tricky. I painted mine so I could see them and make sure that they were seated over the stud and used a punch to drop them on the studs. Then of course comes the torquing in accordance to the manual sequence.

This procedure is probably "old hat" and unnecessary for long time Commando owners but it sure helped me make the job less frustrating.

Just my $.02

Dave

Dave,
Excuse me for sounding dense but did you grind down the box end or the open end? Looked at fitting the 1/4 Whitworth 6box end and it doesn't look like there is much room to reduce the OD. Than again looks like a lot of material would have to be removed on the open end.

Also, where the hell is the 9th head bolt. I found the 2 adjacent to the exhaust valves, the 1 between the exhaust valves, 2 on each side and the nut under the carbs for 8 bolts. Where is the 9th bolt

I think the rolson wrenches must be smaller on the OD. I was at a friends and we had our annual Bring Out Your Dead and I was re torquing someone's head bolts using my friends wrench (same year as mine, 73). I had to grind the snot out of the box end to get it to fit. I ground the box end on mine but not as much. It is also possible that there is casting variation between bikes.

As for the bolts (in sequence of tightening) #1 is the bolt accessible from the top between the "V" formed by the exhaust covers, #2 is the nut accessible from the bottom between the carbs, #3,4,5 & 6 are the bolts around the spark plugs, 7 & 8 are the nuts (3/16 whitworth) accessible from the bottom at the front of the engine sort of above the front iso mount (both sides) and 9 & 10 are the nuts accessible from the top that are in front and on either side of #1.

The first time I had my head off I had a heck of a time finding 7 & 8.

Dave

Thanks at least I'm not the only one ever confused by this

Don't even START to tighten down the head, much less see if the valves actuate in sequence, UNTIL AFTER you use a flashlight and ensure all 4 rockers are sitting in the pushrod cups!

Bought this one used on eBay. 5/16BS = 1/4W. (Not rich - it's my only Snap-on wrench.) No grinding was needed. It's a shorty and works fine on my '72 even with the airbox present.

Why do it the hard way?

1. The center top bolt is the last to come off and the first to go on when assembling.
2. always have the engine at TDC when coming apart or going back together.
3. Have the valves unadjusted but as mentioned the pushrods in the rocker cups.

Thanks for all the advice. I bought the Rolson wrenches seem like a pretty good quality for $50. Although a 1/3 rd of them are larger than anything I need on the bike. Only had the whitworth wrenches that came with the bike and sockets I bought 30 years ago. I'll start grinding down the OD this weekend but sure seems like it will be a tight fit. Might be deceiving though since since it is difficult to see and judge the clearance.

I saw the part in the manual about the pushrods and definitely want to make sure their seated before doing any tightening. I'm fully capable of screwing it up if not careful. Probably more imposing first time than actually will be the next few times I do this.

Dave appreciate the info on the location of the bolts.

Yea, it's pain until you find one of these on ebay. Seller didn't know what it was, but I did.

Grind a little at a time and try the fit, to minimize weakness.

My next door neighbor has a set of obstruction wrenches. Craftsman brand. One of them works perfectly. I have since purchased two different sets(cheap) and neither worked because the outside diameter of the box is too big.

I know this is old hat for most of you but first time I've taken the head off myself. Not surprising why it was leaking. Any suggestions regarding cleaning up the surface, pistons or head? The wire tie method worked great with the pushrods much better than the two women who were trying to push them up into the head.

Hemmings suggests scotchbrite and plenty of solvent in his DVD as I remember.

Dave
69S

Norvil advertise a 1/4" flat ring spanner part no. 069150 which is supposed to fit the rear head bolt, has anyone bought one of these and/or know if it works?

On grinding down box end wrenches. Start with a good quality wrench unless you plan to throw it away later. You want good steel in it. Then grind slowly so you don't over heat it. Quench it often in oil. If you get it too hot it will soften it. You can read up on tempering steel that has been annealed but it is a lot easier if you just don't ruin it to begin with.