Boxerworks.com

Something is wrong with the engine tune. Our race bike was getting in the high 20s, I think 27-28, in endurance races and it was fast.

That compression is way too low. You should find at least 140 lbs per side.

I like my Harley better

mattcfish wrote:

Motorhead wrote:although the motor seems tight and uses no oil or blows no oil it failed the compression check
left 110 right 95

adding oil didn't change the readings so rings are sound

valves settings spot on and motoring didn't seem to point to the cam operation

seems strange but I guess this was comming with the low milage with the sturgis trip to the 20,000 miles after rebuild now 25,000, looking into the chamber through the spark plug hole seemed normal

but will take pulling the heads that were rebuilt at the San Diego outfit advertized in Airhead ABC magazine

maybe just a clean up of the heads..................... who knows just what we are making fuel from these days maybe its the USA getting us to junk these ole bikes

Do a leak down test before you tear anything down.

did you check your valve adjustment?

Valve setting/adjustments were spot on, timeing was spot on

as I pumped up the right I heard a hiss

I didn't hear a hiss but the compression on the left is too low as well 110#

both failed leak down so I pulled the right head and found the intake valve leak so I measured the spring as well its ok
1.810 inch

so maybe just a valve seat freshen up will fix it

Fixing that leak that gave you 110 lbs up to a good number of 140 lbs will not increase the mileage from high 20s to 40 mpg. There is something more wrong. Just my opinion.

Duane Ausherman wrote:Fixing that leak that gave you 110 lbs up to a good number of 140 lbs will not increase the mileage from high 20s to 40 mpg. There is something more wrong. Just my opinion.

Well, he's got to fix the valve leaks anyway. The leaking valves may be throughing is mixture way off on carb adjustment.

when I got 30 with the 37/11 I didn't see no reason to do a motor check when I installed the 32/11.
as the valve adjustments and timeing were a done deal with all systems before or just after Sturgis 3 oil changes 1 plug change and oil filter chage since and yes the puzzleing gas milage that a change to 32/11 was supposed to fix!
I surched the Ohio Cafe site for basic jetting.
My mistake in writeing is Left 110# and right 95#, the right I pulled and found the leaking intake there was no hard deposit
on the valve face or seat just a soft dark stain I used a marker to speed things up gona dig out the lapping paste and see whats up .
maybe the lapping was just done too fast at National City ( High Overturn MFG) the valve guides seem ok and the oil seals are still in place.
I'd just be happy with the 130# I got when I did the motor first time.......
Still whats up??? $580.00 bucks for these R90 heads and 25,000mi later I have to reseat the valves?????
and thats the thing I build it to a Certain spec and that supposed to be a done deal ..then the parts does not go the distance or failed installation inspection....
the LOW mile use of a BMW is certain, asking for trouble.... so I get a second bike known for short travel and decide to use my BMW for longer rides...
Recently I changed out the gearing on my Sportster. And now its smoother and easier to ride further than before, as I just finished it is when Red now FRed had trouble from sitting too long..... All Hydro systems failed as I was getting Him in Shape for Texas then the Pod failed as the electricTach died and the Speedo Didn't match when I bought a 34/11 that came as a 37/11 instead..... so I've redesigned the bike for the last time to a more stock period offering of a 1973 R/5 with certain up grades

I took the right head off and found only a thin line my best glasses only showed a very thin line of rough metel like a scribe both Head and matching valve all the way around

a full hasty surch of my shop didn't turn up my ole paste and sucker stick to dress the offeneding valve, so a trip to the local Auto Zone and 20 mins later I was working the valve, 10 minuts of work was all it took and all markes were gone and tested the valve with pressure and it seemed like it was tight again


so I'm gona dress all of them........ just to be sure

tires used for the trip
Bridgestone S-11 front and back 33# front 42# rear

road kit 45 Lb
25# tank bag
270# suited rider

the Seats in these heads are supposed to be hard for the fuel or specal for unleaded so I'm still puzzled and mistified its always something with these things

Just finished the right side compression dry was 135PSI

so I'll just go to the left side and start there and continue this process


No reason to repost

Just finished the left side and rechecked the right now with my glasses both sides are just over 125PSI not 135psi I just wrote from the fist check

Messy garage

FRed was built to 900cc with Used parts and I think a hopeful wish for 135 is out of the question with used parts

who know when one side or the other went 2 to 4 hours with a side wind as Duane points out in his web site bike will never be the same

puzzle solved

its the amount of throttle

well as I surched for an answer it came to my memory

as I traveled I used more throttle the problem came in a strange way as I fought head winds my throttle was some time about 1/4 from toped out and a try at full didn't do nothing meaning the motor would not pull

then I drop to a lower gear then about the same throttle position but up to the last 1/8th of throttle the motor would not pull

40 MPH

so I began to think the change to a 32/11 was a poor idea as motor power didn't match can fuel be So BAD???

NO! I read other riders with better MPG was where did my power go tappet stabe no valve trouble as it seemed

the Compression check didin't show a so tight motor and the use of throttle to make the motor work that is where my MPG went

I mean to say another idea of BMW operation to look out for

If your throttle is used to an area farther from bottom the usual that is a reason to dig into a motor as well

FRed operated better in the 1/4 to 1/2 are better now instead of the 1/3 to 3/4 I was USEING.