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'88 1000SP - Carburetors tuning

FinkBrau

FinkBrau

Just got it firing!
Joined
Jun 6, 2010
Messages
7
Hi folks,

I have a slight carburetion issue on my 1000SP, the motor turns too fast when on idle, and the motor just can't take it when on full throttle. At first I thought it was just too rich, but adjusting the richness screw changes nothing to the idle rpm.

I tried to follow the instructions of the manual I found on guzzitek.org, which says I need to control the pressure on the exhausts outlets, but the thing is, whatever I do with the idle mixture screw, the left side has always much more pressure...

I don't know much about carburettors tuning, I've never done that before, so some advices would be much appreciated... Here are some additional infos:

- Left carb : VHB 30CS
- Right carb : VHB 30CD


Left sparkplug pic :
BOUG_G.JPG


Right sparkplug pic :
BOUG_DR.JPG



Oh and BTW, I just got my motorcycle driving licence this morning, and I want to ride the fuck outta my bike, BADLY. PLEASE, HELP ! :lol:


Thanks a lot,
Pierre.
 
Check the free play in the throttle cables and the choke cables for starters. ensure the slides can seat and seat evenly with the speed screws turned right out. Then turn in the speed screws until the bike will idle and both slides are hitting them at the same time, then use the mixture screws to produce an even idle on both cylinders.

The idle mixture screws are just that. they only affect the mixture at idle. Just off idle is controlled by slide cutaway, then from about 1/8th throttle to about 7/8'ths it is all down to needle profile and atomiser anulus, he last 1/th or so of opening is controlled by manifold depression and main jet.

Pete
 
Thanks Pete,

I adjusted the slides so they're synchronised, and it seems now that my idle problem is gone. Now I have another one:
When the bike rolls, everything seems ok (didn't try the higher rpms yet, but still), but when I disengage the clutch, and release the throttle, the motor starts to turn faster, for a few seconds. Which results in a big kick in the ass when switching gears. Funny, but not so comfortable...

Any idea?


BTW, a few pics taken this morning :blush: :

GuzzHip1.JPG


GuzzHip2.JPG
 
Throttle cables are hanging up. Re route them so there are no tight bends. You can see in piv #1 that the angle where they go into the top of the carb is pretty acute. You can swivel the carbs slightly, (Not much more than 15 degrees or so.) so the tops point in to wards the centreline of the bike more and this will help but check the enire cable routing and the condition of the cables.

Nice looking bike. First thing I'd do would be piss off the 30mm VHB carbs and fit some 36mm PHF Dell Ortos.

pete

PS, t's not a '88. Roundfins went out of production in about '81 :mrgreen:
 
pete roper said:
Throttle cables are hanging up. Re route them so there are no tight bends. You can see in piv #1 that the angle where they go into the top of the carb is pretty acute. You can swivel the carbs slightly, (Not much more than 15 degrees or so.) so the tops point in to wards the centreline of the bike more and this will help but check the enire cable routing and the condition of the cables.

Nice looking bike. First thing I'd do would be piss off the 30mm VHB carbs and fit some 36mm PHF Dell Ortos.

pete

PS, t's not a '88. Roundfins went out of production in about '81 :mrgreen:
Click to expand...


Yeah already thought about that, maybe one day... ;)

First mods coming are a pair of clip-ons and laser (or water) cut silencer support brackets and battery plate...

About the year, the frame (or at least some parts of it), are from a '88 Le Mans, and the bike is registered as one... I don't know anything about the rest, except that the guy who sold it to me did a really good job on the transformation and engine rebuilding, and was very careful with the bike :)

Anyway, thanks for the tip, I'll try that and keep you updated.
 
It's been riden quite a lot like that, without any problem. These bars go from one point of the motor, to one another, the bars' stiffness is balanced with the motor's stiffness. I've already seen this kind of mod on other bikes.


Anyway, back to my carburettors, it doesn't look like a cable issue, both sliders go up and down to the stop simultaneously. Did only try with motor stopped, though, but I don't think it's a problem.
 
Those plugs look really sooted

Are you sure you are running with the right plug for the engine?

Geoff
 
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