Carbs on an oilhead

[Thunder]

I'd heard about ditching the fuel injection system from an oil head a while back, Steve Scriminger of SED had mentioned it a couple of times and having had work done on various airhead parts through him (carb refurbishments, heads etc) I knew he was pretty thorough, just a little bit fussy, and not one to spin a yarn to get a job

In March someone mailed me a copy of the BMW Club Monthly rag, not being a member I don't get it but it featured an article on Scriminger Engineering and one of the pictures was of my 80 g/s PD, and the subject of fitting carbs was mentioned.

Included in the article was the subject of ditching the fuel injection, it's highlighted in the section below:

PDF's don't convert to jpg format very well so I've attached the actual files for those who want to download them.

Started me thinking so I gave Steve a ring to talk about it, having asked loads of questions, covered the what ifs and buts I decided to go for it, basically he can fit a range of carbs to the bike, rule of thumb being flat sides for BHP, Bing Cv's for torque, having a set reconditioned of 40 mm Bings on the shelf from an R100RS that was the way to go for me. Only thing was I'd sold my 1100 GS to Arsey 3 weeks earlier

Started to look for another 1100 and within a couple of days found another 1100 Anniversary, 2 owners, full service history, 42000 miles on the clock and corrosion free, best thing was the owner would deliver it the 75 odd miles to Steve's place in Sleaford as part of the deal.

Bike was delivered in May, carbs posted over and it joined the queue for Steve's attention, plan was to have it ready for the GOTC at the beginning of June but owing to an electrical problem with the rolling road needed t set it up that was not possible, instead I had to wait until the end of June so decided to fly over, pick it up, head down to the Hogroast then have a few days exploring Cornwall.

Friday the 2nd, this awaited me.

Well that and a box of bits that had been removed, motronic unit, throttle bodies, fuel pump and some other stuff. The 40mm Bings fit straight on to the bikes existing heads and induction tubes, the air box has been altered to handle the carbs and it has a manual fuel tap to control fuel flow. One of the options from Steve was an electronic or manual fuel tap, as I’m used to fuel taps on the Airheads I went for this option, keeps things simple IMPO.

Torque on the bike is amazing, it pulls like a train through the gears and you seldom have to drop out of fifth, other benefits is zero surging, immediate pick up on the throttle and smooth cruising on the dreaded motorways, heading up from Cornwall to Birkenhead for the ferry the bike just purred along, won't say at what speed to protect the guilty but compared to my last bike a significant difference.

Before and after dyno runs show the difference in the torque curve of the carbs compared to fuel injection, bike feels completely different and is brilliant to ride, so much so that a certain Scouser bought himself an 1100 and was on the phone with SED the day after I popped in on the way to the ferry.

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Absolutely love it, like no other oil head I've ever ridden, the 1100's 5 speed box is perfect for this, bike surpasses my expectations, thank goodness I'm off this week, gives me a chance to get some more miles on it.

 

[MattW]

Fantastic - thanks for posting this

I've heard about this conversion before but never seen more than a couple of pictures - great to see that you've had it done and that you like the results. I hope you'll keep us posted about what you think of it.

I've got an 1100 and you've got me flippin thinking now....

 

[Tarka]

Bowser did it a few years ago.

You could possibly PM him for details if you`re interested.

 

[mr badger]

I bloody love carbs I do. The best bit of my 1999 Varadero was the instant pickup and perfectly linear torque curve.

Got me thinking that has.

'twould be rude to ask how much but is it a reasonable amount to pay out, compared to, say a full system and power commander?

 

[MattW]

I'm completely sold on this idea - need to find myself some 100RS carbs...

If you wouldn't mind a couple of questions Roger:

Does the tank have to be modified to allow for gravity feeding the carbs (i.e have an outlet brazed on at the lowest point - I'd have thought the existing fuel supply and return lines on the access cover would be too high up) ?

Do the various RID functions (temp, fuel level etc) and tacho work ok after the conversion (I'm not sure if these are anything to do with the moronic)?

No effect on ABS?

How's the low speed fueling / pick up etc?

I know it's early days yet, but I'd be interested to know how the fuel consumption works out.

Edit: Just thought - do you happen to know if the carbs have to be from an RS or will any 40's do?

many thanks
Matt

 

[Thunder]

I bloody love carbs I do. The best bit of my 1999 Varadero was the instant pickup and perfectly linear torque curve.

Got me thinking that has.

'twould be rude to ask how much but is it a reasonable amount to pay out, compared to, say a full system and power commander?

Well don't want to go into those figures, all I'll say is much less than a full system for your baby

 

[Thunder]

Does the tank have to be modified to allow for gravity feeding the carbs (i.e have an outlet brazed on at the lowest point - I'd have thought the existing fuel supply and return lines on the access cover would be too high up) ?

Nothing brazed on but Steve does a modification to allow for the carbs, not sure what to be honest but it works ok as I have a full tank range.

Do the various RID functions (temp, fuel level etc) and tacho work ok after the conversion (I'm not sure if these are anything to do with the moronic).

Everything works as normal on the RID apart from the temperature gauge which is "fed" by the motronic unit apparently. A work round is being developed for this.

No effect on ABS?

None, ABS fully functional.

How's the low speed fueling / pick up etc?

Smooth and responsive, slow speed control is perfect, not lag what so ever. Pick up is instantaneous and as mentioned not a sign of any surging, bike just pulls cleanly in all conditions.

I know it's early days yet, but I'd be interested to know how the fuel consumption works out.

I'll keep a record just for you, so far the reserve light comes on about 180 miles on a full tank and last fill up on Sunday took 18 litres with 185 miles on the odo.

Just thought - do you happen to know if the carbs have to be from an RS or will any 40's do?

Any 40mm Bings can be used, Steve rejets them for the bike when setting them up on the rolling road, in fact he can do the conersion with mikunis or delortos but Bings are the way to go for torque.

 

[MattW]

Nothing brazed on but Steve does a modification to allow for the carbs, not sure what to be honest but it works ok as I have a full tank range.



Everything works as normal on the RID apart from the temperature gauge which is "fed" by the motronic unit apparently. A work round is being developed for this.



None, ABS fully functional.



Smooth and responsive, slow speed control is perfect, not lag what so ever. Pick up is instantaneous and as mentioned not a sign of any surging, bike just pulls cleanly in all conditions.



I'll keep a record just for you, so far the reserve light comes on about 180 miles on a full tank and last fill up on Sunday took 18 litres with 185 miles on the odo.



Any 40mm Bings can be used, Steve rejets them for the bike when setting them up on the rolling road, in fact he can do the conersion with mikunis or delortos but Bings are the way to go for torque.

Great stuff - thanks Roger

 

[mr_magicfingers]

Very interesting. One of the things I like about FI is that you just don't have to do anything with it, particularly if going to places like the alps where the FI should adjust the fuelling to suit the conditions. Wonder how much maintenance the bings need.

Also, is this limited to the 1100 or will it work on 1150's too? Also be interested to see what happens to the fuel economy.

 

[Stewart H]

Wow! thanks for the information Roger, I read the scriminger article in the Journal and was intrigued, just watch the price of pairs of bings go up on ebay

Stewart

 

[Thunder]

Very interesting. One of the things I like about FI is that you just don't have to do anything with it, particularly if going to places like the alps where the FI should adjust the fuelling to suit the conditions. Wonder how much maintenance the bings need.

Also, is this limited to the 1100 or will it work on 1150's too? Also be interested to see what happens to the fuel economy.

Bings have been on the go for years, been fitted to Airheads so lots of information on them, pretty simple to maintain, easy to access on a BMW, don't need servicing that often, even FI throttle bodies need to be serviced.

1150 can be converted, best speak to Steve though as it's not something I looked into in detail, I know it's possible as I touched on the subject when researching the thing earlier this year.

Steve Scriminger stated in the article that fuel economy was retained with an increase in torque and power, so far thats exactly what I've found even though to be honest I expected mpg to drop.

 

[essjay]

Damn blast..... you have me thinking now....

 

[Thunder]

Damn blast..... you have me thinking now....

This should maybe carry a government wealth warning

If you tried it (which you can do next time your up) you won't be thinking about it, Kenny and Vern both had a go last Tuesday afternoon, Tuesday night Kenny's on doing a deal with Arsey for his 1100 (previously in my custodianship), yesterday this appeared on the site:

Care to guess where it's booked in to have some work done?

 

[mr badger]

Well don't want to go into those figures, all I'll say is much less than a full system for your baby

Ooo. Just what I did/didn't want to hear.

Looks like next years project...

 

[Stewart H]

This sounds like a bloody good idea, I reckon Scriminger is going to be busy

Stewart

 

[mr_magicfingers]

Bings have been on the go for years, been fitted to Airheads so lots of information on them, pretty simple to maintain, easy to access on a BMW, don't need servicing that often, even FI throttle bodies need to be serviced.

1150 can be converted, best speak to Steve though as it's not something I looked into in detail, I know it's possible as I touched on the subject when researching the thing earlier this year.

Steve Scriminger stated in the article that fuel economy was retained with an increase in torque and power, so far thats exactly what I've found even though to be honest I expected mpg to drop.

Thanks for that, will ponder for next year.

 

[ebbo]

Just imagine, 40mm Bings on an 1100RT, fair makes the mouth water

 

[JohnnyBoxer]

Well don't want to go into those figures, all I'll say is much less than a full system for your baby

I think a rough cost estimate would help us to evaluate the pro's and con's in their entirerity

 

[bowser]

for the moment I have gone back to the fuel injection on mine, for a couple of reasons.

Firstly the plumbing is easier with a gsa tank and mine sprung a leak and the plumbing for the GSA tank wouldnt easily fit on the standard tank without a lot of mucking about.
The carbs I had were a bit old and worn and need a rebuild.

But I have to agree with the carbs on, the bike was 100% better at low speed, and went like a train, althougth to be fair I had a bit of a problem around 80-90 were I started to suffer fuel starvation, but I think it was down to my carbs.

The only thing not mentioned in the post is the throttle cable, you have to use R100 set up which is fine, the only problem is that you cannot buy the plastic piece for the handlebar end, its easy to make your own or send the bits to speedy cables and they will make one up for you but the plastic peice is needed as it is unobtainable from any other source, I would suggest keeping any old ones from replaced cables.

you have to keep electonic ignition, (good or bad depends on your point of view) it wil run on the original bmw moronic unit, but there is a good replacement available.

I have every intention of putting it back on again as soon as I have time to do it, or more to the point when I have finished my other bike and can afford to have this one off the road.

 

[(RIP) Mark H]

Just imagine, 40mm Bing's on an 1100RT, fair makes the mouth water

I was imagining, but I think the carb tops would foul the inside of the fairing could always cut holes in the fairing I spose.........