Setting up the carbs on the bumble

Monty

Monty

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Hi again folks,

I have taken the bumble out for a couple of runs and thoroughly enjoying it. I am not sure what the power delivery is meant to feel like on these, so just checking with you.

From tickover nice strong pull, but the midrange feels a bit weak. Almost feels like the acceleration is less on full throttle than part. Then at higher revs it seems to start pulling more strongly. Without a rev counter it is hard for me to estimate what the actual revs are. Overall performance (ie top speed) seems fine, as I was 2-up at an indicated (alleged) 90mph and all felt well. A bit windy, though.

What I am wondering is whether the complete Keihan system (using a y piece) is knocking a hole in the midrange delivery, or if "they are all like that sir"? If it is exhaust-related is there a suggestion (other than buying a collector as I cannot run to that at the moment) as to how best to set the carbs up? I will double check the valves as well as overhauling and balancing the carbs, but I am just working out what to do next.

Thanks,

Matt
 
Only done the balancing twice, but some observations. Tickover is balanced and then at about 3000 rpm. So you could be going from a sweet spot near idle and then back into another later as the cable syncro comes in. My bike doesn't feel like it likes being below 3000 rpm and not accelerating IYSWIM.

From what I've read, the y-piece makes baalncing sub 3k harder, so it probably does affect it below that :(

Try adding a noisier exhaust, then you'll spend more time accelerating and listening to the noise :)
 
I quite fancied THIS, and would be tempted if I had not just got the brand new Keihan. :thumb

I will have a go at the weekend at balancing things up a bit and see if that helps. The R75 was a bitch to balance for some reason, but worth the effort as all of a sudden she was so smooth once things were spot on.

Thanks for your ongoig patience.;)
 
John Armstrong said:
What do you understand by the "R100GS dal 93" in the description?
Click to expand...

Just tried Babelfish and it reckons dal is "from", but I can't understand what is different about the later 100s that would mean it would not fit earlier.

I am happy with the Keihan, anyway, but that pipe does look a good price for a fairly scarce bit of kit. :thumb

Matt
 
Tried the same myself. Tried e-mailing and ebay messaging as like you I can't work out why "from" 93 would be any different as maxbmw parts fiche goes to 09/1994 and it doesn't show any differences from the 90 onwards PD etc :confused:
 
If I had not found the Keihan I would have had a punt at that one and taken a chance. Might be worth an offer at least. I like the Keihan and it seems really good quality, but it (and the original) does have looks that only a mother could love. :eek:
 
Good warranty as well, if they're happy to give a 10 year one, they must have confidence in them. Personally, I think it sounds a bit limp :(

Surprisingly or not, the Sito sounds much throatier on the 100 compared to the 80.

Back on topic, thought about getting a rev counter, occasionally come up on ebay.de, but IIRC Thunder bought one from Motorworks, second-hand, for not too much money.
 
I would really like a rev counter. I will have to make a few calls. That would really help with all the other set up work.:thumb
 
Try adding a noisier exhaust, then you'll spend more time accelerating and listening to the noise :)[/QUOTE]

:likeit
 
They all have a flat spot around 2700/ 3000 revs, and it gets worse if the motor is slightly out of tune.

So , make certain everything is spot on , including ignition timing and float levels and the pin pricks clear, as covered in the tech tips on the Motobins site.

I have the Y piece and feel the bike goes better with the snorkels out- they unclip so it is no big deal to put them back if you dont like them removed.

When mine is spot on I get almost 20km/ litre , and when it drops below I know it is time for a tune up.

However, as there is only a 10% difference between 4 th and 5 th gear it is probably good policy to use fourth gear a bit more and keep the motor spinning .
 
Is yours the Large or small rev counter ??
I think I have a spare large one boxed up in my spares supply :)
Same size as speedo and usually lives S by S with it on the dash of 100/80 GS's..

Also if you don't use the bike regularly, get rid of the fecking oil breather pipes in inlet tract as minute amounts of gunge drip off them and down inlet tract then block middle hole on the carb which is slow running jet intake :(
 
Monty said:
Alas it is a small rev counter I need. :eek:
Click to expand...

A cunning plan may be to get the bike running as well as you can, and then go down to the Gentlemens Wee Kend in June where there may be some small rev counters lying around ;)

I know that you can get handheld revcounters for checking light aircrafts instrumentsa and just like:

http://www.virtualvillage.co.uk/Ite...andheld Tachometer for Engine Rev Measurement

Paint a dot on the revolving bit and it tells you the rpm, just like a phonic wheel. Might be one way of seeing what 3000 rpm is :nenau
 
You can also get a trailtech speedo? rev counter for £78. Not suggesting you mount it but you simply wind one of the wires around the plug lead, another to earth,connect to the battery and fanny's yer auntie.
 
Beemerboff said:
They all have a flat spot around 2700/ 3000 revs, and it gets worse if the motor is slightly out of tune

I have the Y piece and feel the bike goes better with the snorkels out- they unclip so it is no big deal to put them back if you dont like them removed.
Click to expand...

Yes to removing the trumpets it can work, do not have the dyno run with me now.
But with a Y piece and a HPN Baja +KN we had a bad flat spot. Was advised, due to lack of air flow to remove snorkels, Good, but not good enough. Am about to shorten the Airbox internal snorkels to stop cylinder pulsing. ( air sucked towards the cylinder not on intake cycle, taking it from the one that needs it most )And we will likley try a external filter HPN type
Will post jet sizes later.
 
Thank you very much for the info. I will order my carb overhaul kits and get them done, then doble check valve clearances etc and unclip the snorkels. Then I can have a go at balancing things.

With the full Keihan system with y piece and no snorkels, do you reckon I will need to change the needle position?

Regards,

Matt
 
BamBam said:
Yes to removing the trumpets it can work, do not have the dyno run with me now.
But with a Y piece and a HPN Baja +KN we had a bad flat spot. Was advised, due to lack of air flow to remove snorkels, Good, but not good enough. Am about to shorten the Airbox internal snorkels to stop cylinder pulsing. ( air sucked towards the cylinder not on intake cycle, taking it from the one that needs it most )And we will likley try a external filter HPN type
Will post jet sizes later.
Click to expand...
Please explain more about this theory, are the engine specs standard?
Cheers
 
Nippy Normans supply Touratech, Wunderlich, Desert Fox and many other makes of accessories.
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