Himalayan Engine Strip Down and Rebuild

[madbiker]

Part One

As i mentioned in my 1st of January post on my RTW Trip thread in Ride Reports I had an engine seizure that caused considerable damage to the engine. As I was visiting a friend who lives in a very rural area of Northern Spain and who, not being mechanically minded, i had little in the way of a good tool selection at my disposal to undetake this major repair.

As a result of his remote location the ordering and delivery of spares was a long slow complicated process. My workshop was a roofless outhouse that in a former life was a place where animals were kept. Not the best place to carry out the work needed however, I did manage to borrow a bike lift and a torque wrench from a friend of my friend and this made the engine removal much easier.

Okay without further explanation I shall describe what damage was caused, what parts that I replaced and any information that I learned that is not in the engine manual or that I think may be of use to anyone else doing this type of work on a Himalayan engine.

As I had lots of time waiting on parts arriving, I decided to also strip and service front and rear suspension and wheels. As there are a lot of previous posts by other contributors on these particular topics I will not discuss them here. This post will solely be about the engine.

As I am limited to the number of pictures that I can post and if you want to see all of the pictures that I took you can find them here by clicking on this link. https://flic.kr/s/aHBqjzxb3N

I began by removing all of the usual stuff, fuel tank, battery, coil, air pulse valve, clutch cable, exhaust, starter motor, and disconnecting all the electrical connections to the engine. All very straightforward.

I then also removed the framework that supports the clocks and headlamp etc. Again all straightforward stuff.

Then I drained the oil, removed the oil cooler and removed both side casings.







Then I removed the rocker cover, camshaft, and cylinder head. All very easy but just remember that two of the bolts securing the rocker cover to the cylinder head can only be accessed once the tappet covers have been removed.



The cylinder barrel compete with piston stuck inside it came off next and that it when I saw the con rod with the gudgeon pin welded in to it. It was also slightly bent.



The piston had melted and the barrel was badly scored. Both junk.







Then I made use of the borrowed bike lift. I supported the engine with it and removed the bolts holding the engine cradle to the frame and lowered the engine. It was quite a tight fit but after some hefty blows it came apart. Again nothing difficult here apart from the weight of the engine being much more of an issue had I not had the bike lift.



Once the engine was out the bike was starting to look a little weird.



I was now ready to dismantle the engine. My workbench was a raised ledge about 3 feet off the ground which my friend used for his pot plants. On top of this I sat a wooden plinth (like half a pallet) and this was to be my workbench. I will continue with the detailed engine strip down in part 2.

 

[madbiker]

Part 2

Once up on the workbench area I set about removing the clutch, oil pump drive chain & sprocket, and the rotor and cam chain & tensioners.

Initially I tried to remove the rotor with a three legged puller that I borrowed but it was not for coming off. I had no alternative (or so I thought) than to order the RE rotor removal tool (55 Euros) I also ordered the crank gear locking tool and to be honest the removal of these parts is pretty much impossible without it unless you have the facilities and materials to make something similar. To use something else to jamb the gears (like a cold chisel or big screwdriver) would probably damage the gear wheels.

When I was in the bearing suppliers premises ordering my new bearings I saw a rotor puller identical to the RE one on display behind the sales counter for about 25 Euros, so you can get these tools much cheaper than from the RE dealer.



Once these items were removed I removed the main crakn gear, oil pump and gear selector mechanism.



AS I had no intention of disturbing the gear shafts I did not remove the drive sprocket, this helped keep the gear shafts from inadvertently falling out.



I was then able to split the crankcases and remove the crankshaft. and balancer shaft.



The connecting rod is a one piece job and cannot be removed without dismantling the crankshaft which appears to have been pressed together. To get the conrod you need to buy a whole new crankshaft and balancer shaft as one unit. Very expensive.

As you can see in the above photo I wrapped the gear shafts in clingfilm to stop them from falling out or moving too much whilst the crankcases were separated.

As you can also see in this picture the crankshaft has one of the main bearings pressed on to it whilst the other is in the other haft of the crankcase. The new crankshaft also had this bearing pressed on to it and I renewed the other main bearing and both balancer shaft bearings. These were easy to knock out of the crankcases.

This was the oil jet that was loose.



I think that it must not have been fully tightened when the engine was assembled and over the past 28.000 miles it worked loose to the point where the oil was able to bypass the O ring seal and leak out in to the crankcase as opposed to going through the jet and spraying on to the underside of the piston.

I examined the oil pump and although it seemed fine I bought and fitted a new one keeping the old once as a spare.

Once the crankcases were cleaned of any bits of metal and other debris I installed the new bearings, the new crank and balancer shafts. I cleaned the crankcase mating surfaces, coated them with gasket sealer and put them back together.

Thereafter the rebuild and replacement in the frame was a reverse of the removal and strip down that I described in part one.

I also replaced the cam chain and tensioners. I was going to replace the camshaft with a TEC performance one but i was unable to get one, so I used the original camshaft that was undamaged from the seizure.

The reason that I replaced the cylinder head was that as you can see in this photo the valves had been hit and damaged by the piston when it broke and as I had limited facilities to try to change the vales and valve guides in the cylinder head, is seemed more prudent to replace it altogether.



One thing that I should mention here is that when I torqued the main crankcase bolts (3 of them on the rotor side) to the correct tension I found it extremely difficult to turn the drive sprocket by hand. Previously I could easily turn it by hand so I was initially worried that I had nipped something up inside but as the crank was turning freely I pressed on with the re-assembly of the previously removed components.

Since I have owned the bike the gearbox was always a little bit sloppy or imprecise but now it is spot on. It is like the gearbox of all of my previous Japanese bikes. I can do clutch-less changes up and down with no crunching or gears. There are no more false neutrals, no jumping out of gear etc.

It would perhaps seem that these bolts were also not torqued up correctly when the engine was assembled. Either that or the previous owner (I got the bike at 18 months old with 2,400 miles on it) had been doing a bit if DIY tinkering with it. In any case since the rebuild the gearbox is so much tighter and slicker than before.

I ran the engine in over 500 miles. Kept it under 4,000 rpm with no more than half throttle for the first 300 then under 5,000 with 3/4 throttle for the next 100. the last 100 I occasionally took it up to 6,000 and used full throttle when I needed it.

A couple of other tips.

The inner race of the head bearings is a perfect size to use as a drift to knock new fork seals in to place without damaging them.

The wheel bearings, especially in the rear wheel are extremely difficult to get out. I used a concrete anchor bolt of the correct diameter to fit inside the wheel bearing. I tightened it causing it to expand and grip the inner bearing surface. Then from the opposite side I used a socket bar and a hammer to knock the bearing and anchor bolt out of the wheel. Once one was out the other was easily knocked out.

Engine back in the frame with front end removed.



Anyway I hope that this has been informative.

 

[Nader]

Very informative, thanks.
I may have skipped over it, but did you mention why you believe you had an engine seizure in the first place? That thing still looks fairly new...

 

[Robert]

Well, that was some tinkering... at least you now know that it is as it should be.
Where did you get the parts from?

 

[Bluestrom13]

Anyway I hope that this has been informative.

Certainly has - Thanks. (I hope that I never need it!).
PS. There is a freeware program (Converseen) that reduces large photo files without losing quality to any degree, if it might be useful.
BEFORE = 387kb.- And after converseen treatment.= 28kb.

 

[madbiker]

Very informative, thanks.
I may have skipped over it, but did you mention why you believe you had an engine seizure in the first place? That thing still looks fairly new...

I found the oil jet that sprayed the underside of the piston had worked loose and I think that caused it.

 

[madbiker]

Well, that was some tinkering... at least you now know that it is as it should be.
Where did you get the parts from?

There is a RE dealer in Vigo which is the closest one to where I am here in Galaicia. The guy there was super helpful.

 

[madbiker]

Third picture above your post. Description above and below it.
(And mileage - 28,000.)

Certainly has - Thanks. (I hope that I never need it!).
PS. There is a freeware program (Converseen) that reduces large photo files without losing quality to any degree, if it might be useful.
BEFORE = 387kb.View attachment 4093- And after converseen treatment.= 28kb.View attachment 4094

Thanks for the info. Have downloaded it and installed it now.