Rotax Bing Carb help needed..

[95SaxonTour]

Just bought a nice Saxon Tour but she needs some
carb help. the bike hesitates at about 3k while riding.
I heard that these bikes where jetted out pretty lean
from the factory. More than likely to pass emissions.

A carb rebuild is scheduled for the very near future.
So, what jet sizes have people here found more suited
for the road? I live in PA so elevation is not a real
concern here.

Any advice on the rebuild would be helpful as well.

Thanks

[JulianMZRotax]

Hi
I sent this to the MZ Riders mag in the UK. Hope this helps.

Julian




Hi

Well it took a while but I have cracked it. I thought it might be of help to other Rotax 500 owners. Hope you can use it.



Read with interest the article of changing carbs in MZ riders issue 182 by Derek Pickard. Think the problems that I had were to do that the carb was fitted to a Rotax engined Matchless, not an MZ  as the frames are completely different. There is not a lot of clearance.


http://www.flickr.com/photos/57997293@N00/4287793812/



So bearing this in mind you need to buy the cable conversion for the choke. Also you need to have the throttle screw on the LH side. I found out that the mixture screw the Mikunki only comes on one side, you guessed it the wrong side.
Next problem fitting the carb, It's about 20-mm shorter. So go to the breakers with the air intake rubber and carb and find a rubber clamp which fits on the end of the carb and over the air intake pipe. 
To get that extra clearance to fit the carb the inlet rubber on the engine side needs to be turned slightly downwards. The rubber parts now need to be cleaned before joining. Wait until the misses is out and put the rubber parts in a soda solution and simmer for about 3 mins. Remove from the pot and let it dry, when dry the 2 parts can be joined with super glue.  
Buy the way you need to make a shorter throttle cable . Once all the parts are assembled you will find the next problem with the fuel pipe,there is a tight kink. At first I used a plastic pipe and put a small spring inside the pipe to get rid of the kink. I then fitted the original pipe which is a lot stiffer and does not kink.
Well it's been 2 weeks and I still have petrol in the tank. It's transformed the bike it runs much better . Also for the first time I can start it even when cold on the kick-starter, which I could never do before. Thanks for pointing me in this direction.
The carb was bought from the same firm in Liverpool and used the settings and jetting quoted.Love the sticker on the side "NOT FOR AIRCRAFT USE".

Carb Used

VM32 Mikuni 32mm
27.5 Pilot 1.3 turns
2.5 slide
6DH3 needle ,centre notch
P-2 needle jet
185 main
Setting at Sea Level
One other tip for the 500's is if it keeps blowing headlamp bulbs the rectifier is on the blink.

Julian Kowalewski



http://www.flickr.com/photos/57997293@N00/4435088434/


Well I got it in there! It does go a little up hill.

[comanche91]

Just bought a nice Saxon Tour but she needs some carb help. the bike hesitates at about 3k while riding. I heard that these bikes where jetted out pretty lean from the factory. More than likely to pass emissions.

A carb rebuild is scheduled for the very near future. So, what jet sizes have people here found more suited for the road? I live in PA so elevation is not a real concern here.

Any advice on the rebuild would be helpful as well. Thanks

Hi Ryan;

I had the same problem with my SilverStar when I first got it; it had been sitting for awhile. It ran, but lugged badly at anything under 3K. First thing to do is pull the tank and flush all the old fuel, clean the strainer on the petcock, and install a fuel filter when you re-install the tank.

Call and get the basic rebuilt kit (soft parts, i.e. all the o-rings and the diaphragm) from Bing here: http://bingcarburetor.com/otherapps.html . They will ask for the model number; you will need to verify it. It's stamped on the upper webbing on the carb body and the carb has to be removed to read it (at least on mine). The carb should be a model 64/33/304 if it's stock. Order the Bing manual too, it's all you'll need to rebuild it. When I opened mine up I found the the large diaphragm return spring was missing, so you might want to order one along with the rebuild kit. Some MZ Bings had it; some did not. It made a big difference for me on the low end. I kept all the standard jetting but did raise the needle to the #4 slot to richen up the midrange throttle response. It runs great and pulls smoothly from 1K to redline w/o lugging. Here are a couple of helpful sites that can guide you through the rebuilding process. It's actually pretty easy.

http://home.insightbb.com/~cdpumphr/the_carb_chronicles_page_2.htm

http://www.gunsmoke.com/motorcycling/r100gs/carb_rebuild/index.html

[DAVID THOMPSON]

i found on mine it is more ride able with a 17 tooth front sprocket
even a 16 tooth
mine was geared way to tall
making it hard to ride in slow town traffic
dave
also spark plug need changed the d8ea is not the best

below from a past posting
i replaced the D8EA plug with a NGK DPR8EA-9
and what a difference it's like i am riding a different bike
had to reset the idle on the bing carb
and now it runs very nice

[comanche91]

i found on mine it is more ride able with a 17 tooth front sprocket
even a 16 tooth
mine was geared way to tall
making it hard to ride in slow town traffic
dave

Roger that. The Tour is geared the tallest at 2.11 and has an 18T front sprocket. My Silvy was geared at 2.24 with a 17T front sprocket, still way too tall. I swapped in a 16T and it's much better in traffic, and better for the clutch too.

This post belongs in the 500cc section.

[hmmmnz]

hehe, fun times with the rotax
i attempted to change carbs when i was having problems with the float in the bing carb,
but in the end i just couldnt get another carb in there,
so i sorted the bing, and im more than happy with it, although im running a modified xt500 airbox.

i love that with the bing you dont have to unscrew the bowl if you want to dump the gas

[DAVID THOMPSON]

i have found that the rotax motor on mine is not the best when below 3000 rpm
its not a putt putt motor it needs wound up
check my comments above on the sprocket size and spark plug size
and also the spark plug change requires making a cut down spark plug socket
or a very thin wall 18mm socket

the plug change really helps
dave
i am not a fan of the bing carb but make sure its clean and has a good rubber bladder
and a good fuel filter on it