Tuesday, May 3, 2011

Re-assembly & First Ride of the Year

I missed out on the ABCD challenge. I know it's a lame excuse but there were too many things to do on Sunday since I've been out of town so much lately. Plus there were no human shutter releases available. It was a busy day for everyone at home.

Shiny, clean left cylinder head
On Tuesday evening, I finally had an opportunity to install the heads on my '83 R100RT and it was a pretty straight forward process. Anytime you pull the heads you might as well replace the "O" rings that seal the cylinders to the crank case. It is also a good time to replace the pushrod tube seals since they tend to get hard and brittle with age and heat. The easiest way is to put the pistons at top dead center then carefully pull the cylinders until you can get to the snap rings holding the wrist pins in place. Remove one of the snap rings and push out the wrist pin until the connecting rod is free. Then pull the cylinder off leaving the piston in place inside the cylinder.

Right cylinder connecting rod
The cylinder must have been off before since there is red RTV (silicone sealer) on the pushrod seals. This wouldn't have been done at the factory and is not recommended. This must have been done by the previous owner to take care of an oil leak. Cleaned up all traces of the RTV and simply used some assembly lube to help ease the new rubber parts in place. Put the cylinder back on followed by a new head gasket and the head. If you look carefully at the first picture, you will notice that the head gasket isn't symmetric. The exhaust pushrod tube is a little farther from center due to the exhaust valve being slightly larger than the intake valve. Put in the pushrods, reassemble the rocker arm assemblies taking care to allow just a little bit of side to side play on on the rocker arms when installing the rocker mounting blocks. Torque the head bolts to 24 ft-lbs in three steps in a star pattern doing each cylinder when it is top dead center compression stroke.

Left cylinder
Adjusted the valves, replaced the tupperware (lowers were removed earlier to get better access to the cylinder), re-installed the carbs and exhaust using plenty of high temperature anti-seize on the aluminum exhaust nuts. Put in the spark plugs with more anti-seize, turned on the gas petcocks and fired it up. It started up immediately on the first revolution and had that familiar BMW airhead sewing machine sound suggesting to me that the valves were adjusted properly. After letting it warm up and checking for oil leaks, I cleaned up the tools and headed to bed. Too tired for even a short test ride.

Tomorrow I'll check all the fluids, air up the tires and finally take my first ride of the year. This is the first time I've ever torn into a motorcycle engine. The Airhead tech days we started having this last winter were a great opportunity to see what was involved. One of the members needed to replace the push rod tube seals on her '95 R100RT. I still need to replace the fork boots but that involves dis-assembling the forks. Another evening perhaps.

Wednesday - This afternoon, I finally went on my first ride of the year. By noon, it has warmed up to about 50°F from an overnight low in the high 20s. After adding a bit of air to the tires, I took off to get a fresh tank of gas. There is still an incredible amount of gravel and sand in every intersection. Even the end of our subdivision road was gravel from edge to edge. The university has been thatching the grassy areas and flinging all the dead grass and dirt onto the roads. Lots of road hazards. I still managed to get in about fifty miles before stopping at the gas station. Here I noticed that the front master cylinder was leaking a bit. I guess I didn't tighten down the cover screws which hold the reservoir to the master cylinder. Tightened it up and it looks good. I guess I'll need to keep an eye on it. The engine ran well and after maybe a hundred miles, I'll re-torque the heads and adjust the valves. Then again at about 500 miles.

As usual, I feel like I need a bit of low speed practice again and all the gravel means slow going through the turns.


  1. Wow Richard, you are quite the wrench...you make it sound pretty easy and I am pretty sure there's plenty of ways it can go wrong....great job.


    Redleg's Rides

    Colorado Motorcycle Travel Examiner

  2. RichardM:

    It's scary . . . I am not a mechanic but as I read through your words, I understood what you did. It's great that it also managed to start, right away. I am sure it gave you a lot of satisfaction.

    Riding the Wet Coast

  3. Hooray!

    Enjoy that first ride of the year. Hope it is a sunny one.

  4. I've assembled small block chevy engines, but never been in a motorcycle engine, yet. Helmet is off to ya. You're becoming quite the wrench.

    Enjoy the first ride of the year.


  5. Great job, Richard! You're the man! Congratulations! Looking forward to hearing about the first ride.

  6. Huzzah! Bike is back together, running, and even taken out for an awakening run! Great job and big round of applause for not having any left over parts and only minimal bleeding. :) No pictures of her on the road? :(


  7. Thank you for the comments on my mechanical aptitude. I have been working on vehicles for years and was once a dealer mechanic repairing Mazda rotary engines. One of the real attractions of the old BMW airheads is their simplicity. Very old school. No electronics, no cooling system, pretty simple bike. The hope is being able to fix whatever happens to break. The trade off is poorer brakes, significantly less power, and you can't just take it in to someone for repair.

  8. Impressive. I wish I could understand and do only half of it. I would be the lady of the wrench!

    Welcome back on the road. Hope to read ride reports very soon. Ride safely on those gravel roads.

  9. Dear Richard M.:

    You make this sound as easy as switching out a pair of hand grips. From your description, you would think the heads, pistons, and cranks are waiting to jump off into the cleaning solution.

    So I armed with the enthusiasm I got from your blog, I tackled a job on the K75 that I have been meaning to do for some time. I pulled a wrench out of the tool box, knelt down next to the bike, and screamed, "What am I doing?"

    Thankfully, I stopped in time.

    Fondest regards,
    Jack • reep • Toad
    Twisted Roads