Hello, I have the dreaded sprag clutch issue and no rocking of the bike in gear will release it.  Before I have to go internal I wanted to clarify a few things.  Some talk about using cleaning fluid but from what I read that is bikes with intermittent issue that can get them runing and hopefully clean everything up but I cant even get a start.  Can I clarify if I can fill the whole engine space up with cleaning fluid so it covers the sprag clutch and will hopefully remove any gunk/crap off it?  If anyone has tried this what was the best product (I am in the UK) how much did you need and how long did they leave it for?

Thanks in advance

Hi Wilbo,In the event that you cant start/ride the bike youtube has some good videos, one shows removing the crankcase cover to gain access to apply cleaner.
As for cleaners,flushing oil or similar will work.Hopefully greater minds on forum 
will offer advise.PERSONALLY with the usual DISCLAIMER,i would drain engine oil
and fill to max with DIESEL shake tilt push etc DO NOT ATTEMPT TO START.Leave 
overnight drain.replace filter fill with flushing oil.and bump start if necessary.
Finally once running ok change engine oil to a DIESEL engine oil this will realy clean the internals.

Don't fill the whole engine.

You can't start it with the key, but you should be able to roll start it. With engine oil and half a litre of diesel mixed in, you could let it idle for five minutes or so. Or the diesel engine oil idea sounds good too.

I've heard of guys having sprag troubles from using synthetic oils; What are you using? How many miles on clock? Did it start acting up all the sudden or progressively get worse? Did it only act up when cold?

Research Rislone

Fuchs oils/lubricants uk.Whilst working on site i enquired (as you do)Whats the best oil for my K AND WHY.Quality Mineral oil MUST be used.NEVER!!NEVER!!use semy/full synthetic oil.They research it make it sell it and know more than me.
ME?,i do as i'm told,and its a damn site cheaper

Others prefer full synthetic.

As do I. Mobil 1 for choice. Although my experience is with 70s air cooled bikes (airheads and Brits) and early water-cooled OHC car engines.

Post #74 on this thread shows you how to clean it by spraying carb cleaner or such. Just remove the Crank cover. Pictured is the k11/16v engine I hope it's the same on the 8v.

I had the sprag start slipping on a 16V K100RS. Caused by using too much moly assembly paste when doing some work on the head.

If you can do a bump start, put a half liter of an engine cleaner like Seafoam(diesel fuel will probably work as well) in the crankcase with fresh oil.

Bump start the engine and go for an easy ride, this is not an Italian tune up.  After about 25 miles, stop, and change the oil and filter.  Use a good heavy duty diesel 15w40 oil.  I don't think Synthetic will hurt.  Shell Rotella T6 is good and can be had reasonably inexpensively.

contact cleaner with a probe tube bent at about 90 degrees can reach into the oil filler hole , pointing the previously bent tube on the contact cleaner slightly towards the back of the motor -( from right angles ) and slightly up
can work

what your trying to do is swamp the sprag clutch outer drum , usually some of the fluid will penetrate the holes built into the outer drum which retains the sprag fingers , to release the gunk build up


just a short spray (about 2 seconds ) wait a few , then another spray of about 2 seconds then wait a few minutes (15 -20 ) before trying to start

the contact cleaner disperses the grunge collected in at least the area that you have sprayed ,

the high whatever content it is , evaporates quite readily and wont affect much anything else

I have done this quite a few times with success , usually after a longer than usual non riding period - or after a particularly cold spell - change in weather

in fact just last week again with the change in weather to pretty damn cold , and the low ride events associated with the corona lockdowns out here .


I am about to change the oil in the engine , as its reached its 5000k due date , to that diesel - petrol compatible engine oil available for the next oil change

in the past , by doing this , I haven't experienced sprag slips for some while after , of corse after doing the oil change a good run of a few hundred kilometres lets the cleaning action of the oils to work best

good luck !



.

Wow, some fantastic reponses and advice on here.  Regarding this issue I have a feeling it came about due to injector issues I was having, the bike had become a pig to start nearly flattening the battery every time I tried.  I had checked and changed the temp sensor and when I pulled the injectors I had one decent spray pattern, the rest were sticking and I had only just had them proffessionally cleaned in the last 500miles, I think I have been letting the bike sit to long.  I have had this hard starting issue twice and both times once I had the injectors cleaned it started and ran like a new bike for a short period of time.

Anyway the oil stunk of fuel as it was just washing down the bores so I drained oil replaced filter with 10w40 (and it was semi synthetic so I wont use that anymore!) and it was a horrible brown/white colour from the fuel mixed in it!

This bike has been a pain since day one!  Although it is 1986 I traced it via the frame number and it is actually a 1983 model that was used as a shop display bike until it was registered in the UK in 1986, it only has 30 odd thousand miles in reality on it but has had a clock changed due to them packing up.

As this model has the old sprag clutch design and the 6 rivet output shaft I may bite the bullet yet and try another engine.  Come on convince me to persevere!! 

Again a big thanks for all your thoughts on this forumn.  As an aside note as lockdown has lifted in the UK i managed a run out on my 1980 honda goldwing that I restored yesterday into the lake district where I live for my daily exercise, beautiful to be on two wheels again!

I also have a 1983......its got the early camshafts and you are not going to find a later one having them. There is no comparison against the later engines. I have an 84 K100RT, later cams and its good but the 83 engine despite shortcomings is brilliant.

Open it up, change the sprag clutch and rear main seal as you are there and ride on grinning from ear to ear.

Just asking as I now have wheel off, drive shaft out and having a brew before I tackle the next bit removing the gearbox.  I am going fully internal as they say!!  I would rather do a full strip and clean than run risk of a partial clean and I have time on my hands to do this.  I will do rear oil seal as also advised with bike being 37years old!

Anything else I should do whilst in back?

Code:

I will do rear oil seal as also advised

And the 'O' ring while you are in there.

If you can get hold of some 8mm dia stud you can make up a couple of supports to help when removing/installing the gearbox.  Remove two mounting bolts and screw in the studs to act as 'rails'.

I have a couple in stainless plain bar, threaded just enough to get a good depth for support. The plain bar means no exposed thread to catch on the box.

Mike

Right, this bike is killing me now!!  Sprag clutch cleaned and repaired and engine turning over beautifully.  Not starting though and noticed no sound in fuel tank, fuel low enough I could get crocodile clips on feed to it and I am getting 0 volts.  Checked tank connection took it off and cleaned it still no volts, even pulled cables out and tried on spare fuel pump I have nothing.  Swapped computer control units over as I have 2, nothing so I am thinking fuel pump relay, any ideas or other checks I should take first??

Have you checked the fuel pump connector that you would disconnect to remove the petrol tanks. It is a common fault that the female side opens up, giving a bad contact.

Mike

mike d wrote:Have you checked the fuel pump connector that you would disconnect to remove the petrol tanks. It is a common fault that the female side opens up, giving a bad contact.

Mike

Hi Mike, I have now tested further and it is blowing the 7.5amp sixth fuse down.  I will tighten the under tank connections and also test for voltage with it disconnected.

2 stuck fuel pumps would you believe it!  Put them onto wooden blocks and direct 12v to them and they do nothing, I may try stripping one down to see if I can free one.

Positive progress!

You could try reversing the leads to see if a jolt backwards can free the pump.

Mike

Probably wouldn't hurt to put some penetrating oil in the pump(from both directions) and let it soak overnight.

Point-Seven-five wrote:Probably wouldn't hurt to put some penetrating oil in the pump(from both directions) and let it soak overnight.

Yes, I have done that overnight but its not playing today at moment, will leave for longer.  I have ordered another pump as if i can free one of these off I shall keep it as a spare.  This bike has been one of the classic stood around and lots of issues once retored.  Once I get it running again I am going to ride the tyres off it initially to see if I can get it to be reliable.

The biggest issue I have had with it has been fuel injectors, on my second professional clean.  I have fully cleaned fuel tank out again now and fresh fuel that was when I hit the sprag clutch issue!!  Glad thats sorted now.  Fuel injection reminds me why I like carb bikes!!  Simple!

Day 1 - So I thought I would post my final outcome to returning to running service.  My new fuel pump arrived and I fitted it, bike would not start or sound like it would even catch.  I pulled the injectors and found only 2 squirting fuel, took the all off cleaned them in work proved all flowing and put back on bike.  Bike would try to start and then die, did not like fast idle but when I cranked it with throttle fully open and then shut it off bike sounded like it was going to catch, just as battery was about to die it started so I kept it running jumped on it and did a quick 50miles with it running like a dream.

Day 2 - Went out to bike in garage on battery tender tried to start not interested or sound like going to catch, went through throttle on full then off and it started on about fifteenth attempt, again jumped on it and put another 50 miles, pulled plugs and good colour, checked injectors all squirting nicely.

Day 3 - Went out to bike and checked battery voltage which was good, tried to start once not interested then remembered I had put a new temperature sender on it over a year ago and these can cause starting issues, checked pin 10 and it was showing well out about 300ohms, remembered I still had old sender which had not failed but I changed as it is 37 years old and thought I will do a quick test pulled plug off one on bike and put it on the old one that was just hanging free and.......................bang starts first time and runs idles like a dream!!!  So I swapped my 37 year old one for my 12month old one and bike is officially happy and I have a running machine!!!  Moral of story if it aint broke dont try and fix it.........

Thanks for all the help and advice over my last escapade, maybe now I can enjoy my bike for a bit without wrenching on it and cursing electronics!!

Hi wilbo,a happy ending to a horror story,NICE,now for many happy miles

Temperature sensor faults can be caused by the application of thread tape or sealant. The sensor earths through the threads. The sealing is achieved with the soft metal washer. Dirty connections can also come into play, especially at the sensor which can cop a lot of road spray and crap.
Regards Martin.