loss of power

[makkit1]

recently purchased a 600s divvy, looks like the bike had been stood outside for a long time. rode it too work when i first brought it after 5 mins it started to splutter then cut out. i have done the obvious procedures, took the carbs apart cleaned them out, checked the fuel tap for blockages, checked pipes for any leaks or kinks, a new fuel filter. put everything back on gave the bike a good run took it up to about 9000 rpm, then same again loss of power. waited a couple of mins gave the tank a good shake, got going again after 5 mins same again. rang my local yamaha dealer he said the carbs need a proper clean out, £40 for his service same again this time after about 3 mins. having looked at other members posts i can't think what else i can do, could a new air filter help? rubber carb inlets? or recon carbs? please someone help!!!!!!

[Padster]

One of the common problems is a blocked breather in the petrol tank. It stops fuel getting through. When it stops open the filler and if you hear a slight woosh then this would be the likely cause.

[makkit1]

is it actually inside the tank, if so where would it be located?

[bobh]

I may be wrong, but I think it doubles up as the overflow - one of the connections with a rubber pipe leading down behind the gearbox. The rubber pipe may have got kinked when refitting the tank at some stage.

[amorti]

What they said, particularly if the bike has been standing. There is a small hole in the "lip" under the petrol cap. Identify it, and blow some compressed air through. Once it's more or less clear, you can even use some little pipe cleaners to do the job properly. If it rusts through or you poke or blow it through you have a problem as fuel will leak out, so be as careful as you can!

[makkit1]

many thanks for your advice, i had a check and the pipe seems to be clear. in fact i replaced the rubber hose as it was perished. i'm convinced its fuel related, a friend of mine thinks the carbs need syncronising but would this make the bike cut out?

[marshallman72]

I'm been having what sounds like the same problem. Thats why I'm here, looking for help meself. I've made some progress. I'm at a loss to explain how it got there but I've traced the problem to water in the fuel tank!!!!!! I drained the tank, then swilled it with paraffin. There some corrosion in the tank as small bits of rust came out (I removed the fuel tap). I drained the carbs, after I'd cleaned them out once!!!, they were half full of fuel, & half full of water??!!! The bike now starts and runs. Once warm it goes, however I'm convinced that something is still wrong as the idle is very lumpy. At idle its more like a 2 cyliner engine. There is a constant rhythmic thumping present and the initial pick up is a bit fluffy. Also, the revs take a little longer than normal to fall again after closingthe throttle. All 4 plugs are firing cause if I remove 1 at a time, you can hear the difference in the idling. Might I have to clean the carbs again?

[amorti]

Did it look a bit like this? I think the problem is it's very easy to kink the drain pipe as you put the tank back down onto the bike. Worth sticking your hand in and checking it's free each time you have the tank off and on again.

Your other problem sounds like there might be an air leak in the carb rubbers. How did they look when you took them off? They seem to be weak on divvy's. I never touched mine while I owned the bike as they looked like they'd crumble. M+P have some cheap if it is that. You should probably also just turn the idle speed up. In cold weather Divvy's like to idle around 1200. Being an air-cooled motor, they don't much like cold weather as the motor runs cooler and all tolerances are bigger. Well, that's what I was told, I just know it idled safer at ~1200 in winter.

edit:
It could also very well be the start of carb-icing season,. If the heaters aren't working perfectly (and sometimes if they are) Divvy's can get this bad. Cure it by adding ~1% Isopropyl Alcohol (IPA) to your fuel at each fill-up. I used to keep a pop-bottle in my top-box.

[bobh]

When you cleaned the carbs out did you make sure the pilot jets were absolutely clear? They have tiny little holes in them and are easily partially blocked by residue from old petrol. They should gradually clear with running, and some IPA in the petrol will hasten this.

[marshallman72]

I've had the carbs off again. Pilot jets & pilot air jets are all clear. Floats on carbs 1 & 3 were very very slightly higher than 2 & 4. All the same now. The thumpiness is still present at idle, however the pick up from idle is fine, dare I say it improved a tad over what it was before the troubles started. The only thing I haven't tried is checking the carb balance since cleaning them. Iwonder how fussy they are, ie if you remove the carbs from the motor does it upset their balance? I do wish the manufacturers would fit single or twin carbs on middle of the road fours!!!

[marshallman72]

It lives!!!! In the end I purchased a Gunson colourtune. its basically a glass top spark plug so you can see the charge combusting in the motor as it runs. I've used them before to good effect, but suprise the ones I have already are the wrong size! Anyhow whilst idling a regular blue flash is visible on all cylinders except number 3. Hardly any flash at all. So straight away I identified the problem carb. Before tearing into the carb again, I thought lets just check the carb balance. They were well out!! Needless to say, upon balancing the carbs, all the trouble went away. Just goes to show you never stop learning.
Also having checked and confirmed all carb adjustments are now correct, the engine does not like the choke when starting be it cold or hot. I see a nice regular light blue flash from all cylinders. If I set the idle speed to 1200rpm when warm, the motor will start from cold with no choke, and idle steady at about 500 rpm. If I put the choke on, it won't play ball. Whether or not things will be different when conditions are really cold, well only time will tell. Is this choke situation a case of "they all do that, Sir", or is there still some underlying problem?
On a different matter, does anyone out there know where I could get hold of some better ignition coils without breaking the bank? Nothing wrong with the coils themselves, its the HT leads. They appear to be sealed in the coils. One of the plug caps keeps coming off the end of the HT lead, & the lead core seems to be soft so I'm struggling to screw the plug cap back in to it. I'd like to change the leads for the old type copper core leads, because they're more robust and longer lasting, but if the leads won't detach from the coils, I'm kinda stuffed!! Any thoughts?

[amorti]

Are you sure the leads are sealed into the coil? are they not more likely to be threaded in, same as at the other end?

Coils are coils, you just have to find better ones that fit the gap, do you have a friendly breaker local to you?

[marshallman72]

Hi there!

I'm not certain the leads are sealed in, but compared to 2 other bikes I'm familiar with, the coil/lead meeting point looks different. On an old Honda 350s I had, & a GPZ500 my brother had, there was a gland nut securing the leads in position. On the Divvy, there is no gland nut. I don't want to rag the leads out, only to find theres no way to get them back in!
The only suitable aftermarket items I've found so far are the Dyna coils. Different coils have different primary resistances. I'm guessing if you fit one with the wrong resistance, it'll knacker the black box. Yamaha spec a resistance of between 1.98 & 2.88ohms. A dyna at 2.2 ohms would do, but they are very expensive. Most Suzukis seem to run 3 ohm coils. I reckon a Kawasaki one might do. on flea bay theres a pair of 2.2 ohm dynas off a gpz900, still beyond my price range! It seems a pair of Kawa ones at 2.2 ohms with 90mm fix centres would do. A helpful breaker local to me may be able to help, he has most things I've ever needed. If anyone here knows where I might find some, let me know. Thanks!!