Hi guys, i'm a newbie K100 owner, purchased a non runner with electrical fault to restore during UK winter.  Anyway I sorted the electrical fault in 24hrs, starter motor needed polishing up and I have the bike running, starts first time and sounds lovely!  As i'm going to take frame away from engine and have it blasted and painted I thought I would do an initial compression test before I check valve clearences and see condition of engine incase I need to carry out any engine work when I have the oppourtunity.

I warmed the engine up, then carried out the compression tests and all circa 80-85psi!  Does anyone think valve adjstments will make a huge improvement?  I'm going to take cover off and check clearences but I am not convinced.  As my bike is a 1986 model i'm thinking it maybe a leaded/unleaded valve issue on the cylinder head, any views off you experts?  The bike says 42,000miles and is in good condition for 31years old,does not look like it has had a hard life but as we all know many a clock failed!

Any pointers for me??

Thanks in advance

All circa 80-85 suggests either the gauge is defective, not correctly sealed or not fully tightened home to seal it. Consistency suggests this is a strong possibility and try another gauge before worrying about the outcome. A check on valve timing might be wise too but try another gauge frist.

I think 86 should be ok for leaded fuel too.

What Olaf says.

92KK 84WW Olaf wrote:All circa 80-85 suggests either the gauge is defective, not correctly sealed or not fully tightened home to seal it. Consistency suggests this is a strong possibility and try another gauge before worrying about the outcome. A check on valve timing might be wise too but try another gauge frist.

I think 86 should be ok for leaded fuel too.

Thanks for reply, I shall carry out another test tomorrow.  More worrying though is the fact I have followed a link to when bikes were manufactured from this website, it appears mine may have been registered in 1986 but manufactured in 1983..... My frame number is 0003361 which points to bike being manuafactured between 10/83 & 11/83 which I think means it should be for unleaded.

Mine also is the earlier one and has just short of 80,000 miles and runs ok on the unleaded fuel. I think unless you are riding really hard this will not be an issue.

Dai has a lot more mechanical knowledge than me!

92KK 84WW Olaf wrote:Mine also is the earlier one and has just short of 80,000 miles and runs ok on the unleaded fuel. I think unless you are riding really hard this will not be an issue.

Dai has a lot more mechanical knowledge than me!

Hi, thanks for reply.  I have just confirmed also from the engine number that it was built in week 43 of 1983 so is designed for Leaded.  I dont inten to use it to hard but I am going to give it a full restoration and was also intending to use it for touring on, would not want a burnt out valve in the middle of no where!  I may have to continue using my R100RT for that.  I may also look at getting a topend from an unleaded one if I can pick one up.

I would have been more worried if one of the cylinder readings was way off, that would point to a problem in that particular cylinder, possibly valve but a badly burned valve would lead to very low compression.

Don't come to any conclusions without another test, redo it maybe but also go for another gauge and come back to the forum.

If memory serves me right its about 10.2 to 1 or about 150psi.

wilbo wrote: My frame number is 0003361 which points to bike being manuafactured between 10/83 & 11/83 which I think means it should be for unleaded.

What is your source for the information that this engine is one of those designed for unleaded, wilbo?

I've racked up almost 45,000 miles on mine in the last four years. I did a valve check at about 75,000miles (it's now at almost 85,000 miles) and found nothing wrong. Mine's a November '83 model.

Dumb question here, but are you holding the throttle open for the test?  If not, give that a try.

Another thing, is the air filter clean and the MAF flapper swinging freely?  Any rodent residences in the airbox?

good point .75  wot (wide open throttle ) is required for this test

Point-Seven-five wrote:Dumb question here, but are you holding the throttle open for the test?  If not, give that a try.

Another thing, is the air filter clean and the MAF flapper swinging freely?  Any rodent residences in the airbox?

I love dumb questions!!!  It's 2 years since I did a compression test and totally forgot to open the throttle!  Just been out, ran bike to temperature and carried out test again.  Here are my results

Cylinder 1 - 135psi
Cylinder 2 - 135psi
Cylinder 3 - 145psi
Cylinder 4 - 145psi

May have ran the starter a bit more on last 2 cylinders but the compression does not look that bad to me for a 33 year old bike!!

Thanks for all your help fellas, much appreciated.

With those readings I think I would be putting the tester back in its case and carrying on with riding the bike. 145 is about 10:1 and I cant see it being worth doing anything other than checking valve clearances. I thing that's all I would do and carry on riding.

What is nice about the forum is that somehow the right answers come out. The first readings were fairly consistent across all cylinders and it would seem that your K is indeed a nice one.

92KK 84WW Olaf wrote:With those readings I think I would be putting the tester back in its case and carrying on with riding the bike. 145 is about 10:1 and I cant see it being worth doing anything other than checking valve clearances. I thing that's all I would do and carry on riding.

What is nice about the forum is that somehow the right answers come out. The first readings were fairly consistent across all cylinders and it would seem that your K is indeed a nice one.

Hi Olaf, thanks for the reply.  Yes I was a bit shocked to see the huge increase in compression, almost to specification as in my Haynes&Clymer manual.  I almost agree I maybe just creating a load of work for myself dropping engine out to get the frame blasted and painted, but the bodywork has lots of scratches and chips on it also which lets it down and I like to have a nice looking bike.  I may just put it in for an MOT out of interest and see what happens!

The engine casings look in fantastic condition and I know it was well looked after as the last owner had it for 10 years and was meticulous in his maintenance, splines, oil/filter, fuel/filter etc etc and always stored inside.

I could just put it on road for spring and use it for a year I suppose to see if it does have any issues before I tear it down.

You could probably describe me as anal-slothful.  I like to have a nice looking bike, but would rather not kill myself getting there.

Instead of dropping the engine have you tried cleaning up the nasty spots on an individual basis.  One of the worst is under the tail cowling.  I have been very successful masking off and doing touchups on the frame using Rustoleum satin black from a rattle can. 

You can do one spot at a time, usually in a day or two, and be off riding in between.  Keeps the rust at bay, and the frame looking good for a minimum investment in time and cash.

My RT looked a bit sad when I got it.

Swapped the heat shield with a spare I had for the LT, it needed a piece cut ut but looked a lot better than the battery acid damaged one I took off at the time.

Cleaned and repainted the frame on the battery vent side, over the heat shield, it was badly acid corroded and used a brush paint in satin black. Will do the rear under the rear cowl this year and replace the seat lock with a nice new one that came courtesy of BobT in 88's travel bag. I have done some other parts of the frame as Point Seven Five suggests, a nice day and do it outside on the patio.....and enjoy the ride in between. Would I drop the engine to paint it? No way, not when we can ride all year.....I would differ if we couldn't ride in winter.

92KK 84WW Olaf wrote:My RT looked a bit sad when I got it.

Swapped the heat shield with a spare I had for the LT, it needed a piece cut ut but looked a lot better than the battery acid damaged one I took off at the time.

Cleaned and repainted the frame on the battery vent side, over the heat shield, it was badly acid corroded and used a brush paint in satin black. Will do the rear under the rear cowl this year and replace the seat lock with a nice new one that came courtesy of BobT in 88's travel bag. I have done some other parts of the frame as Point Seven Five suggests, a nice day and do it outside on the patio.....and enjoy the ride in between. Would I drop the engine to paint it? No way, not when we can ride all year.....I would differ if we couldn't ride in winter.

It's not that bad a bike really and if i'm honest i'm going over the top, mainly because I want to!  I've plenty of other bikes to ride but I have a feeling i'm going to like this one a lot!  Especially if I can find a decent screen for it for touring.

I take it that yours is a K100 basic from the numbers showing up, 10/83.

There are some screens available and others on the forum might have more information on these.

But a thing to keep in mind is that RT/LT fairings are rather effective for touring and they keep coming up for sale. You would need a few other items with such a fairing, change of handlebars, clutch cable, throttle cable, front brake pipe from the master cylinder, headlight. This would be great for touring.