What's this tube from CV carb? 660 Skorpion

[Petrolhead]

Hi, I'm a new Skorpion owners so pardon my ignorance. Bike won't run without the choke on, so I thought it would have a clogged slow air jet/passage or an induction leak. I found this tube venting to air from the CB carb body, any idea if this should be so. There is a filter mesh unit which is the drum like part on it. The previous owner said that parts of the vacuum tap units were taken out to aid starting.

And any ideas about this part, it does not appear to be on my bike:
http://www.ebay.co.uk/itm/MZ-MUZ-SKORPI ... Sw0vBUdKDP

Any ideas folks?

[KevinLS]

Was there a photo attached showing the tube from the carb? I couldn't see it. Things which immediately spring to mind are the "hidden" filter in the carb float bowl. If that is blocked then you will have all kinds of fuel starvation problems. It's an easy fix. The other thing is whether the tube you are talking about is the one which is normally connected to the fuel pump. I took my pump off and discarded it, but you do need to blank the vacuum hose in that case. If you can post a pic I may be able to identify the Thos you mean. I don't have that fancy canister on mine either, I have never seen one.

[Petrolhead]

Sorry, I didn't include the pic. Here it is:

[KevinLS]

That vent is OK, it is supposed to be open. When you say that the bike only runs with the choke on, what are the exact symptoms? Does it run OK, right through the rev range when the choke is on, or does it only run at small throttle openings and low revs? If it is the latter then it's a good indication that the small filter in the float bowl is blocked.

[Petrolhead]

It starts up first or second press of the button on full choke and will after 30 seconds on full choke ,will allow the choke to be backed off till it runs at 1600 rpm plus with the choke nearly off. As it runs it misfires back through the exhaust and spits back through the carb with mild pops and burps and if the choke is backed off it stops quite quickly, won't continue to run.....I'm taking the carb off this evening to clean and check it. I'll try cleaning the jets and passages with carb cleaner and compressed air.

Otherwise it runs right up through the rev range as long as the choke is on, revving happily, I quickly stopped running it one evening when I saw the headers on the exhaust glowing cherry red!

[dandywarhol]

The "choke" is a fuel enrichener which only operates when the throttle is closed. Once the throttle is opened the enrichener is bypassed - so the fact yours runs ok with the "choke" on is ok - it isn't actually doing anything.

Sounds like a carb stripdown and clean out should help. Also a good time to check the condition of the intake stubs for cracking, leading to drawing air.

[Petrolhead]

Hi Dandy/Kevin,

Got up early today and did the carb strip, clean and refit. It was so nice to be able to get them on and off with no hassles, just the back airbox rubbers were a bit fiddly. It starts up fine now and runs without choke very well , in fact I have been able to get it to idle around 1200 rpm well. Pilot screw is 3 turns out, I found an oring in my parts box to replace the rotted one on the needle.

Looks sorted now, thanks for the help

[DAVID THOMPSON]

check idle specifications do not idle these engines too slow
its hard on them

DAVE

[Petrolhead]

That's funny, I was feeling that the engine wasn't too happy at 1200rpm, so after reading your post I have upped it to 1350rpm. The SZR660 manual says 1300+/- 50 rpm, would that be OK? or does it need to run slightly faster?

BTW the pilot jet and other parts in the carb had gone off fuel the consistency of light/medium oil on them and the fuel level was about 5mm to low. says a lot about the strength of the engine if it would run at all

[dandywarhol]

Good to hear. Ethanol in the fuel is the problem these days, causing water to form in the passageways. It also rots the rubbers

[DAVID THOMPSON]

i got a bad load of gas a few years back and had to wash out the tank on the rt125

it was like olive oil

what a mess
only time i had to haul a bike home from a long trip
lucky me it was only 50 miles out from the house and the stepson came and got me
dave

[Petrolhead]

Thanks for the input......I believe that Esso Super here in the UK has no ethanol additive so i'll make sure to fill up with that from now on. In the past I have put fuel stabiliser with standard supermarket unleaded in my Honda 4 tank and its been fine , but I really like the 660 and want to make sure its fine long term

[dandywarhol]

Esso Super contains 5% - 10% for standard fuels