Setting up the carbs on the bumble
- Thread starter Monty
- Start date
Beemerboff
Registered user
Snowbums site has some useful items , and a lot of pure codswallop.
Take her list of absolute truths on exhausts .
My R75/7 runs great with a two into one, and an unequel one at that.
But dont try it with a stock muffler and standard intake system as Snowbum probably did.
San Jose BMW extracted around 5 more HP out of a R100GS with a Supertrapp, removing the snorkels and tuning the carb , yet the bum couldnt get them to work.
Most eveything I have read on induction length tuning places the distance from the inlet valve to the carb as the critical distance, not the overall length.
The overall length does matter, of course, but changes beyond the carb have much less effect than those before it.
Yet this guy claims to have got 8 hp more by changing the snorkel length.
He doesnt seem to have even tried changing the carb to head length.
FWIW my low compression GS with a Y piece and a slightly derestricted stock muffler runs best with the carbs as close to the heads as possible, the snorkels removed, the breather tubes removed from the intakes, a Unifilter, the fuel 26 mm deep in the bowls and a little less advance than stock.
I was thinking of playing around with the trumpets in the air box too,as if you add their length to the length if the connector tube the total seems pretty long, but I try and make only one change at a time and I havent reached it yet.
The r100 GS goes well - I had no trouble seeing of a F800S the other weekend and they are supposed to have 86 HP.
Probably has , on a dyno , but you dont use a bike on a dyno.
Take her list of absolute truths on exhausts .
My R75/7 runs great with a two into one, and an unequel one at that.
But dont try it with a stock muffler and standard intake system as Snowbum probably did.
San Jose BMW extracted around 5 more HP out of a R100GS with a Supertrapp, removing the snorkels and tuning the carb , yet the bum couldnt get them to work.
Most eveything I have read on induction length tuning places the distance from the inlet valve to the carb as the critical distance, not the overall length.
The overall length does matter, of course, but changes beyond the carb have much less effect than those before it.
Yet this guy claims to have got 8 hp more by changing the snorkel length.
He doesnt seem to have even tried changing the carb to head length.
FWIW my low compression GS with a Y piece and a slightly derestricted stock muffler runs best with the carbs as close to the heads as possible, the snorkels removed, the breather tubes removed from the intakes, a Unifilter, the fuel 26 mm deep in the bowls and a little less advance than stock.
I was thinking of playing around with the trumpets in the air box too,as if you add their length to the length if the connector tube the total seems pretty long, but I try and make only one change at a time and I havent reached it yet.
The r100 GS goes well - I had no trouble seeing of a F800S the other weekend and they are supposed to have 86 HP.
Probably has , on a dyno , but you dont use a bike on a dyno.
Hi folks,
As usual, I am a bit confused. I am now not sure which way to go with the set-up / tune of the bumble. I don't know whether to leave or remove the snorkels, and I am also not sure whether I need to change the needle position to account for the lack of snorkels and the y-piece?
I think I should still order the carb kits from Motorworks, though, to make sure everything is lovely inside those Bings.
Matt
As usual, I am a bit confused. I am now not sure which way to go with the set-up / tune of the bumble. I don't know whether to leave or remove the snorkels, and I am also not sure whether I need to change the needle position to account for the lack of snorkels and the y-piece?
I think I should still order the carb kits from Motorworks, though, to make sure everything is lovely inside those Bings.
Matt
Carb tuning is not straightforward. I would say that if you have a problem with a bike that is standard in most respects then dont make any changes until you have it running perfectly. After that it may be worth experimenting with, but from what I have read and tried and looked at you have to start spending bucket loads to make any significant HP improvements. I have changed to Mikuni carbs and I think the bike runs better. I would spend my money on making it work as best it can as stock e.g. good quality valve guides and three angle valve job but that’s only MHO.
I've got a Y piece on mine. Got to say I'm not impressed with it. When I put the bike on the Dyno the tuner wasn't impressed at all.
Some stuff here -
http://www.ukgser.com/forums/showthread.php?t=157857&highlight=Dyno
The Embarrassing 37BHP and jetting problems turned out to be the cam timing out by one tooth. Reseting the timing has helped a lot
but I still think the Y piece buggers things up.
Some stuff here -
http://www.ukgser.com/forums/showthread.php?t=157857&highlight=Dyno
The Embarrassing 37BHP and jetting problems turned out to be the cam timing out by one tooth. Reseting the timing has helped a lot
but I still think the Y piece buggers things up.
I dropped by to see my mate Bob from Tabikes (local airhead geezer) and he had a quick peek into the carbs. It transpires that both pilot jets were blocked and their o rings were falling apart, and once he had blasted them through and popped on some new o-rings things are much more promising.
The low to mid-range, part-throttle response is now much better and I am finding my bumble to be brilliant fun.
Next job is to do the valves and timing and then balance the carbs.
The low to mid-range, part-throttle response is now much better and I am finding my bumble to be brilliant fun.
Next job is to do the valves and timing and then balance the carbs.
I'm sure I've read somewhere that the intake trumpets for the air filter should be the same diameter, but can't find where 
I can't tell from: http://www.ukgser.com/forums/showpost.php?p=1718911&postcount=8 if they are or aren't
Any piccies to show if they are aren't? TVMIA
I can't tell from: http://www.ukgser.com/forums/showpost.php?p=1718911&postcount=8 if they are or aren't
Any piccies to show if they are aren't? TVMIA
I dropped by to see my mate Bob from Tabikes (local airhead geezer) and he had a quick peek into the carbs. It transpires that both pilot jets were blocked and their o rings were falling apart, and once he had blasted them through and popped on some new o-rings things are much more promising.
The low to mid-range, part-throttle response is now much better and I am finding my bumble to be brilliant fun.
Next job is to do the valves and timing and then balance the carbs.
Usually due to gunge coming from the blasted breather pipes
Beemerboff
Registered user
Quote- Usually due to gunge coming from the blasted breather pipes
Yup , that is one reason I have re routed the breather to a catch can.
The other was to see if removing the silly bit of plastic pipe from the inlet makes any difference.
I think it does
Yup , that is one reason I have re routed the breather to a catch can.
The other was to see if removing the silly bit of plastic pipe from the inlet makes any difference.
I think it does
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