Power loss question

[steve hawkins]

The position of the needle needs to be moved down, which means the clip needs to be moved up.

The needle position will effect the mixture at 2/3 to 3/4 throttle - and will move fully out the way at full throttle - at that point it is only the main jet that is in play.  I think there are on 4 positions on the needle.  If the mixture is too rich at this point then the motor will bog down - some people notice it as a 'flat spot', for others it is worse....But you do not want to run too lean, but then you only have 1 or two positions to move to...

I also had an after market exhaust - it looked the same but sounded different.

I had this issue when I first had my bike - took me years to figure it out - I went rich (and made it worse) long before I went lean - even bought bigger jets  .  I am now using standard jets and needles.  Just positioned my needle in a slightly leaner position.

I hope you have success.

Steve H

[Tv]

Success, sort of.  I moved the needle position to what I think is the leanest ie, the very first position on the fat side of the needle.  This way the needle sticks further into the jet?  I now have a flat spot around 3k but if I gas it it quickly pulls through then through the 4-5k range and onto redline (not that I take it that far but it seems it'll go)
Got back from a quick test ride around the block and noticed oil coming from between the block and the cylinder head.  

That wasn't supposed to happen!!!!  Better get the tension wrench out

[goomicoo]

I feel your pain. I replace to pushrod seals and now it leaks more! And just to pile it on, I left the petcock on for a couple of days (duh) and now it won't idle and i's fowling plugs. Aargh, I work on this bike way more than I ride it.

[nhmaf]

TV - It sounds like you might be onto the problem, there - I didn't think from your description that your exhaust system was different enough from stock to impact the mixture, but apparently it is.

Goo - maybe you have a leaking seat in your carb jet, or you've got a stuck float, from having the bowls overfilled with gas when the petcock was left on.      Also, check your engine oil to see if you ended up with fuel getting into the cylinder and down into the crankcase.  IF you smell gas from the dipstick /fill hole or the level shows that it is somehow higher than normal, you gotta drain and change the oil and oil filter or risk damage to the engine.

[steve hawkins]

Have you a Haynes manual?

As far as jetting goes, I know the jetting recomendations are different for UK/European bikes than those in the US.  I forget which side of the pond is leaner.  Are you still running the air bleed pipes?  Or have you removed them?  

How old are your needle/jets?  If they are originals, and you have any sort of mileage on the bikes, then a new set of standard needle/jets might be in order.  They do wear, and when they do they will make the bike run richer.  At least we are getting there though.

You might also find that changes in gasoline might also be implicated? - a wild stab in the dark, I know.  But there is no doubt that gasiline from the early 80's is different to that we are running today.  For better or for worse.  

[Darwin_R65]

Welcome to the world of 28 year old motorcycles !!!!

Thanks - I sold my Harley because I felt I couldn't tinker with it and it was costing me too much to own.

Harley "a way of life",

because you spend your life fixing them ?

 

[Tv]

The needles and jets are new.  The exhaust has a connecting pipe on the headers at the front of the bike but not underneath.  The 81 has the connecting pipe underneath.  Which is standard? I've been running High Octane 98 Unleaded fuel so I might try standard unleaded and see if that makes a difference.

I have a Haynes manual but it can be vague in some areas.

[MrRiden]

OK WAG* time. Wadda ya think of too large of a main jet and a float set too low. Yea I know 2 carb sets were tried but were the jet sizes ever verified as correct? From experience I found once that floats I was 'dead sure' were correct were too low to a more practiced eye. So a rich main makes the plugs black but the low floats cause fuel starvation at high [sustained] revs in top gear. Once the high speed is attained the float bowls have a chance to catch up and the motor runs OK again.
rich

*Wild @$$ Guess

[Tv]

All good theories, BTW what are the air bleed pipes which you refer to Steve?

Hey Darwin, I had that Harley for over 2 years and so far it was the most bullet proof bike I've ever had.  Never let me down, went like a scalded cat and never used, sweated or dripped oil - pretty boring huh?  At least with these BMW R65 bikes I can muck around with them and if I mess something up it's no big deal.  How's that Valiant go?

[steve hawkins]

Tv - its an American do-hicky for emissions.  Some complicated pipe-work between the airbox and exhaust.  

You probably wont see it in Oz - I should concentrate more.

I would check you float heights as MrRiden suggests as well.  

Its a fiddly job but worth persevering with.

[tagordon]

Apologies, did not read the second page before posting.
My vote is for floats and/or fuel flow too low.
Ok all, correct me if I am wrong.
No mention of abrupt stalling or dying of engine, leads me to believe problem is in the fuel system. Most probably the float level is a bit low.
While adjusting the float level is a good time to check fuel flow. If the flow can't keep the bowls filled it'll starve.
I had similar experience after rebuilding carbs. 1mm up or down makes a big difference. I went up untill it started dying on me when braking, because the high fuel level was sloshing into the venturi. Then slowly backed it off untill not stalling at all.
If ignition is the cause I have experienced a back fire usually.
The black fuzzy looking plug may be from raw gas entering the venturi.
Just throwing this out there as even with new floats it is possible they are not set just right. Or not enough flow to keep the bowls filled.

[Tv]

Looks like I better have a go at the floats (have been dreading touching those)
I was riding last night after tightened the head bolts and re-checked the tappets and realised that 0.01" is NOT 0.1mm (der!!!) and set them right then re-adjustied and balanced the carbs. It runs very smooth until it gets to the dodgy rev range then stutters a bit but powers on through, then I ran out of petrol.  Once I sorted that out it behaved a lot better but it's still not quite right.  
With all the fiddling I'm convinced it's a fuel thing and floats are the only thing I haven't messed with so here goes :-?

[drewboid]

One other thing to check - the metal insert at the top of some of the bing carbs can leak air around the edge and mimic a diaphram problem. Sometimes you can just catch a fingernail at the edge of the disk. Bike will run fine up to a point and then run out of power for the last 1/3 of the throttle movement.
Fix - run some thin epoxy around the edge of the disk sealing the slot. Some riders glue on a coin or a BMW logo.
Easy fix to try - minimal cost and nothing to take apart!

[steve hawkins]

Did we ever get to the bottom of this?

Have you managed to fix your issue?

[Tv]

G'day Steve, sorry about the delayed response but I've been busy with work and putting the old '81 back together and have been neglecting the troublesome '84.
I checked the float levels and they seemed OK to me.  I still cant get the thing to run right.  It idles fine, I take off and it glides to 3k revs and dies then splutters for a second and, because I have to give full throttle, eventually takes off.  Very annoying in traffic.  When cruising at between 80-120 kph it seems to fade so i give it some gas and it goes ok again. Erratic behaviour - makes it tedious to ride.
When I tuck in and give it the full bore on the open road it seems to be starving at full throttle but when I back off a bit it'll accelerate so I've got used to tickling the throttle until I reach the desired speed then wrestle with it to 'stay'.  Seems to go to 140+ no problem usingthis technique
It does also sound like it gurgling when I back off, maybe a bit of a back fire.

I've reassembled the original 84 Bings and I am refitting those in the near future. I have a timing light stored away under the house somewhere and I'm going to see if I can check the timing.  Will need to find out how to do that; and I think I may need to seal the exhaust system properly as it may be leaking a bit.  Only a few things huh? [grin] but I am determined to figure it out.  I'm still trying to find that level playing field

Hope you are all well and life treats you good