Boxerworks.com

Well as I asked for help

I can see from replys(or lack of) your as puzzled as I am, I know when I pull the heads again I will find the coating I been talking about although no other Californian has replied or told of the same problem???

I use no additive just Chevron locally and certanly and Valaro when I'm on the road even Texaco, but no one even thinks in that area so.......

Its a old bike, And as I told Duane I won't sell it maybe its time to rethink and bail it may cost 1000.00 to rebore and buy pistons and gaskets and send my heads to some BMW Guru that may or may not fix it.... as the cause is not Idenified and a 1000.00 CHANCE....

25,000 miles to date.... maybe started well before as the milage was on the way down during Sturgis ride and the change of gearing to a higher ratio didn't help......

So 2000.00 will get some lucky fellow

32/11 with a 95 percent spline with a matching rear wheel, San Jose fork brace, San Jose 5 speed kicker tranny with 25,000 and clutch with 25,000
a Motor with 100,000 mile crank and 312cam Newer Mikuni 32 jetted right DynaIII a 1977 subframe and swing arm with the driveshaft damper adding life to the tranny Custom fitted San Jose Brace progressive springs with a bottom spring instead of a bumber works rear shocks Corbin seat

Lots too much to explain extra tranny extra gaskets shims parts oil/air filters.... tools ect I'm Done ..... bring a truck

Ditto M/C service is finished...........

Have you worked out why your compresion is so low? What size is the engine, 750,800 1000?

If you upped the engine size, do the heads match the pistons? For example there are 6 or 7 different 1000cc pistons and at least 3 different combustion chambered heads. Haveing the wrong combo will be a huge power and fuel robber.

You've got probably the easiest vehicle in the world to do top end work and a full piston cylinder swap on.
Do not dispare. Good used heads are compartivily cheap if worst comes to worst.
You said that leak down tests confirmed that the valves are leaking and nothing else. There's only a few things that can cause this.
Improper adjustment (too tight), burnt or bent valves, poor seal do to wrong cut or lapping, or loose valve guides.
Adjustment (done on the compression stroke?) hasn't cured the problem. When you lapped the valves they produced a nice wide even grey ring on the seats right?
Did you check the play at the guides? I had bad guides once.Sometimes the bike would ride fine and other times it would burn oil and gas. It probably depends on the head temperature and expansion variables. If the guides aren't guiding properly then the valves hit the seats off center. All the lapping in the world won't fix that.
You don't have to pay big bucks to have your heads reworked (if it comes to that). All you need to do is find a reputable shop in your area. Talk to a mechanic that is involved with racing to get a recommendation. Supply the shop with all the official specs regarding seat angle and guide clearance and see what they say.
I had my seats cut and new guides honed for new valves for around $150 a couple of years ago. Buy all the parts yourself to make sure you get the quality you want.

1 head's cost 580.00 and sold as rebuilt unleaded heads
2 cylinders/matching pistions sold to me as firsts and under 60,000 miles so easly passed the measurments and simple hone and dry break in with new rings
3 lapping gave a nice wide gray all around and home test proved no leak after the work and all paste removed as it was water washable
4 I have owned this bike for over 9 years and done all maintance some custom work tune ups etc don't need no vacume stick or other device to balance the bike just hands smell and good very good ears
5 hasting rings and all parts I used before and had sucess some parts were not as advertized or delivered and most were kept as the seller said I was a cheat or trying a lie
6 1000 dollars to do this again
7 I am motorcycle certified so maybe as we don't or sometimes agree I have my reason
8 quality is personal and although some engineers can do the math tis the attitude I find repulsive

also valve guides are new look new and fit as suposed to, and like I said the seat and valve face has a coating like peanut oil cooked dry on a fry pan

also I use .006 on intake and .008 on exhaust and my feeler guage slide smoothy on every setting and the test for spec.... is always sound and still as set no closeing gap

and again the bike is a 1973 R75/5 modfied to 900cc (R90S) piston 1974 spec with a 312 cam 32mm Mikuni which at rebuild finish came in at 135 PSI and today is under 120 PSI and leaking out the valves

Motorhead wrote:and again the bike is a 1973 R75/5 modfied to 900cc (R90S) piston 1974 spec with a 312 cam 32mm Mikuni which at rebuild finish came in at 135 PSI and today is under 120 PSI and leaking out the valves

Do you have the parts to put your bike back closer to stock? Your engine, in effect, is highly modified. If you have the parts maybe you want to put it back to near stock, and if the problem is still there, you were going to sell the bike anyway. Those parts, especially the cam and mikunis, ought to sell well through ebay or some other venue. The result would be that you will be getting significantly more money than selling the bike as it is.

My thoughts anyhow.

Ken

at 87,000 the bike suffered valve recession so it was then I decied to up grade to 900cc I traded and sold the topend or used parts in my business

the carb replacement came from the Bing bore wear out I twice time happed during BMW ownership the Mikuni was a cheaper and good choice to do and as I think this problem came sooner than 25,000, I just didn't think I had a problem and as the bike had power and does perform the bings were just changed to Mikuni at 18,000 the bike had about 20,000 before the trip and just had the 32/11 installed

Also it should not matter what cam or rings or other arrangement if you spend the bucks for a rebuilt head the heads should be sound so even if I had the other heads what answer should I get or answer you be looking from me

the bike uses no oil and as other airhead bikes come to be around you cannot hear no differents some say my motor is much quiter than theirs

I beleve the cylinder and rings is sound so what in fuel is causeing this my 32/11 should be giveing me over 40 MPG but 25 is not good