Low power???

bigkev

Guest
Three years after first getting my GS (1100) it's stopped working as well as it used too and despite trawling this site for potential fixes I'm all out of (affordable) ideas and my budget to fix it seems only to get smaller.

My problem started last year when out on a short run my bike started to lose power after about ten miles, I continued after topping up with petrol but by the time I'd done 20 miles the power was right down. I was visiting friends and was there for a couple of hours before completing the return journey which pretty much went the same way, from cold it was ok but after having completed the 20 miles home I could barely pull away from the lights.

I've tried many things and on occassions it's seemed better but it ain't right!
I've changed the TPS (brand new), tried a different coil, HT leads, ECU (second hand and untested) and plugs (brand new-also untested!!), I've checked the tappets (OK), compression (7 bar rising to 8, same on both cyls) and throttle balance (OK when cold but a slight difference-about 1/2 inch-when hot), the injectors look OK but when cranked doesn't give a fine spray (?), the throttle cable is seated but does run real badly on the frequent occasions I forget to put it back correctly, also checked the fuel ( no water) and fuel filter (new fitted), the coating/paint on the inside of the tank was breaking up and peeling away so I removed all that was loose and cleaned up the gauze fuel pick up, there was a problem with the off-side injector wiring, but I've replaced that by grafting on a new section, I've even changed all the relays.

For those who have got this far, thanks, I would of given up before the end of the first paragraph. I'd be grateful for any further advice, especially if it gets my bike going again.
If theres not much in the way of things to check, suggestions as to who to take it to somewhere not to distant from Aylesbury, (that's in Bucks) would be a great help.
 
I presume its nothing daft like the clutch slipping is it ?.From what you have previously tried,it would be obvious to you...but you have to ask.
What's the plug colour like ?.Are they sooty from a rich mixture?.
Does the engine rev cleanly not under load?.
I know the hall effect sensors can give problems on the 110,but i dont know if they give the problem you are describing.
Can you spin the rear wheel easily when it seems to lose power?.
Check for binding brakes.
 
Thanks for the replies.

Colban
Fair question but not the clutch, I've had that before! The plugs are that wishy washy beige that they're supposed to be and I removed them after a short run the other day and they were dry and looked OK, it does run (it's been a while since it last ran well) off load with little or no sign of the low power and the wheels run freely. From your hint I'll cross hall sensors of my list.

Steptoe,
You got me with that one, I did have it in mind that the fuel pump may have been the problem but don't know anything about the fuel pressure regulator.
Any further info about it, location, difficulty, availability and cost would be of great interest to me, of course if I thought it would get that far I'd be in a South London workshop in a flash!
 
Thanks for the replies.

don't know anything about the fuel pressure regulator.
Any further info about it, location, difficulty, availability and cost would be of great interest to me, of course if I thought it would get that far I'd be in a South London workshop in a flash!
You know how you have to burrow into the bike to get to the clutch...
Well,you dont have to go quite that far.Its between the airbox and the gearbox.

http://www.maxbmwmotorcycles.com/fiche/MainDiagrams.asp?mospid=47944

Have a look at it here.Select 16,Fuel supply.
 
If it runs OK for 20 miles or so - could it be a blocked fuel tank breather creating a partial vacuum and starving the fuel pump ?

I'm not sure of the arrangement on the 1100 but see if opening the filler cap resolves the problem (for the next 20 miles).
 
Cheers, not seen that website before. I guess somewhere in there there'll be a clutch too!

I got all excited when I discovered one of the little pipes from the fuel tank blocked but sadly it was the water drain not the breather, but it all makes the 1100 with carbs I saw at the weekend an attractive and simpler proposition
 
Just got back, all running like a dream again!

Many thanks to those who helped.

Too close out the thread-almost, I managed to get hold of a second hand fuel pump, regulator and injectors which I fitted also changed the air temp sensor, one of these things caused my bike to feel much better. I may start putting some bits back just to clear it up in my mind, if I do I'll let you know. (I'm sure that the legendary Steptoe will be proved right)

Total cost in parts;
TPS, ECU, injectors, air temp sensor, relays, fuel pump, pressure regulator, coil & leads, bits of a loom, manual, vacuum gauges and gaskets studs o-rings and the like-£375ish.
Cost in time; too embarrased to say
Benefit; learnt a whole load about my bike.

Would BMW done it any cheaper???

Now all I've got to do is change the split rear gator
 


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