600 Divvy Driving me Mad!

Watty100

Watty100

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Hi Guys, My son's W reg 600n has been stood for a while while he's been trying to get a full licence. Last time I tried to start it, it was really rough, found out it wasn't firing on No3 cylinder. Stripped and cleaned the carb, blew it through with air-line (having recently done all 4 carbs), it was very reluctant to start, eventually fired up, still on 3 cyls, as it warmed, No3 came back to life, but bike wouldn't rev when the throttle was opened. As it warmed more, it would rev, but with a delayed action, both in spinning up and slowing down. After about half an hour of running, it started to run fine, gave it a run up and down the street, all was well! Except that after I turned the bike off and let it cool, when I started it again, it was mis-firing again, not as bad as at first, but still enough to make it hard to ride. I ran out of time but think it would have gone OK again if I let it get hot.
Any thoughts as to whats wrong would be much appreciated, Thanks :mad:
 
You say 'not firing'. Was it? Or was it / is it not getting fuel? Have the plugs been changed? Check the basics before buying new jets or carburettors!
Ducati 750/900SS are great for just what you describe and the owners say yada yada... Yet a pair of new plugs has it running. As Kaister says - new fuel too. Eliminate the cheap stuff before looking for expensive problems.
 
make sure all the carb rubbers are seated correctly,fore and aft of the carbs,check they are all nipped up tight and that you havn"t dislodged any from the air box.put a couple of litres of 97 octane in it and maybe a drop of fuel system cleaner (redex or suchlike) if it seems ok take it for a decent run,if youre going to leave it stood again then run nearly all the fuel off before you park it up.
 
Should have said, tank has been drained and fresh fuel in. Carb rubbers checked and double checked for leaks, plenty of easy start sprayed around the potential leaky areas and nothing found. Plugs, oil, filter, air filter all new.
When I say "not firing", there was a spark to No3, but when I took the plug out and let it tick over, there was no fuel or smell of fuel coming out of the plug hole. Just to confuse me even more, there was fuel in the float bowl when I took the carb apart again.
Plugs, oil, filter, air filter all new.
I've just dragged it out of the garage again and fired it up, again it started very rough (on the choke), couldn't touch the throttle without killing the engine, which improved as it warmed up until it ticked over and revved quite nicely with just a hint of a misfire. Would way out valve clearances cause this?
The Reddex sounds like a good idea (and cheap!):confused:
 
have you checked the diaphram in the number 3 carb for holes or tears? try cleaning the connections on the coils.swap the plugs about,might be a dodgy plug.then you might be looking at getting the carbs ultrasonically cleaned and checking the valve clearances
 
Also check the carb choke pins are all sitting down properly.

No fuel to one carb could be the fuel pump is weak. Try hot wiring the fuel pump. If its the vacuum type chuck it out.
That all said, run the fuel tap on prime and see it it helps. Thinking aloud the fuel tap has a vacuum diaphragm maybe that's affecting things.

Wide valve clearances will clatter. Too tight kill the compression so its unlikely to run at all. The only way to know is a compression test.

On another level, old bikes can often have problems with corroding wiring connectors. Go though the wiring loom with a fine-tooth comb and clean any connectors that are dirty, loose or otherwise questionable. Some connectors are only there for factory assembly purposes and can be chopped out, soldered and heat shrink sleeved.
 
A mate of mine had a similar problem with a fazer that had been standing for a while. it took three goes with an ultrasonic cleaner to get all the gummy deposits out of the carbs. Sounds like you eliminated most other potential causes. The guy said Yams were prone to the carbs gumming up-don't know why that would be.
 
mpjbiker said:
A mate of mine had a similar problem with a fazer that had been standing for a while. it took three goes with an ultrasonic cleaner to get all the gummy deposits out of the carbs. Sounds like you eliminated most other potential causes. The guy said Yams were prone to the carbs gumming up-don't know why that would be.
Click to expand...

proper carb clean needed would be my guess too.
 
Now running

The Divvy is now running on all 4, after a total strip of the carbs and some new bits. Engine sounds good BUT it still ain't right, when you open the throttle, it revs up quite freely, but stays revving high for several seconds before settling down again, even though the throttle is closed.:barf
Any thoughts out there on what to check, before I start the hunt for a new set of carbs:nenau
 
Perhaps Idle mixture screw setting is maybe wrong, it is CV carbs isn;t it ??

Too rich and she will run on a bit

Did you do a compression test to make sure the pressures are about even in case she's drawing air at an inlet valve ??

I've just finished one gallery linky

It took ages to sort this bike out Basically from the feedback from the guy who did the valve guides, The inlet valve seat on the right side (The compression gauge can be seen in the photos if you want a look ) was virtually eliptical and the two exhaust guides were very reluctant to let go! Three goes in the oven!

Anyway what we fathomed out is that the air leak was causing that cylinder to run very lean and that's very likely what over heated the exhaust valve causing it to crack.

We couldn't fathom if it was the seat wrecked the guide, or, the guide wore and made the seat elliptical It was touch and go for a new valve seat :eek:

Out of them all it was the worst with about 3 to 4 mm of free play in the guide when in the open position, the rest of the valve guides were "serviceable" but the owner wanted them all changed!

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Bottom Line

Check that the pressure readings across the cylinders are pretty much the same

it could save you a lot of dough later

I know with those it's shims but a lot cheaper than a dropped valve!

Safer too
 
SORTED

Thanks for the tips gents, bike is now up and running with a new secondhand set of carbs. I can only think that the gunge from the tank has blocked up more of the carbs than a simple blast with an airline will fix :thumby:
 
so lets just recap.

Bike was running perfectly before it was put away with fuel in it.
Strangely, it won't run right when re-started months later.

Was it the valves suddenly developed cracks or went out of clearance ? No.
Was it the carbs miraculously unsetting their idle jets ? No
Was it the plugs suddenly closed up , faulty or anything else ? No
Was it the carb diaphragms suddenly getting holes or the rubbers perished ? No.

it was ....wait for it...the fuel going off. ?

What ? No way ? impossible..thats just madness.........:eek:

Is it me ? :rolleyes:
 
MJPBiker got it bang on. The carbs were gunged up, most probably still have some gunge blocking some circuit or other, which is why it didn't run right. The gunge looked like orange jelly, and had totally blocked the little filters behind the float needle seats on a couple of the carbs. The tank also had rust inside, a consequence of ethanol being able to absorb water, I believe.
Now working to de-rust and seal the tank and hopefully get the bike back on the road soon.
 
In the 90s I had an XJ600 which ran like a bag of spanners after lying for 6 months, turned out to be rust in the tank choking the filter on the petrol tap, always worth a check when suffering fuel starvation.
 
Kaister said:
drain all the fuel and put new fuel in .
Click to expand...

Agreed. Modern fuel gels after standing for a fairly short time, my old Triumph struggles after being stood for more than a month. You really need to drain all the fuel and re clean the cards. Having said that it may well be something electrical but I'd start with the fuel on the basis that starting with the cheapest most obvious suspect is the sensible route...

Dave
 
Nippy Normans supply Touratech, Wunderlich, Desert Fox and many other makes of accessories.
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