Gs550 odd tickover

[RETROHOWLA]

1977 GS550 on vm carbs, fitted with later electronic ignition and coils.

Recently rebuilt my mates GS550 on a very tight budget, basically the only new parts were a cam chain, spark plugs and full gasket set.
Head skimmed, valves reground, reshimmed valve clearances, 15000 mile barrels and pistons and a dam good clean out and check over.

Put it all back together but its not quite running right, basically on tickover it doesnt seem to be firing on pot 1, take it for a run though and it pulls clean and strong on all four pots.

I have tried, new plugs, checked the spark and all good, swapped the coils over, double checked the valve clearences and had the carbs apart and given them a thourough clean and blow through but there was nothing to suggest the carbs were even remotely dirty (i had them sonic cleaned last year)

Now the only thing i havent checked is the carb balancing and will be doing this tomorrow when i dig out my balancers but was wondering if anyone had any other thoughts on what it might be if this has no effect?

Any ideas would be greatfully recieved

 

[Nessism]

The pilot jets are prone to plugging up since the orifice is so small. It's standard procedure to hold them up to a light to make sure they are open. Not sure what to suggest other than this and the carb sync you already mentioned.

 

[RETROHOWLA]

Yes the pilot jets have all been out and checked in this manner, none showed any signs of blockages what so ever, thankyou for the thoughts though.
I am hopeing a carb sync will sort it but as we all know these odd little issues sometimes take many hours of head scratching and fruitless spannering.
Im starting to go bald from all the head scratching!

 

[RETROHOWLA]

Well a carb sync done and it idles a bit better but still seems a bit off on pot 1?

It starts on the button though and ticks over without too much complaint so i think im going to put it down to 70.000mile engine and carbs that just arnt going to perform like new anymore!

 

[hampshirehog]

This is very common on the 550s with their 2 jet in line pilot system. 99% of the time it's a tiny bit of muck in the second (smaller) jet. What makes it more difficult to detect is that you can clean the jet and look through it and see light so it all seems fine. What happens is that the bit of crud gets stuck to one side of the jet and you can't see it. Only part of the crud is actually 'glued' in place, the other part is just sitting on the side. When the fuel starts to move through it 'floats' the unstuck part of the crud up to block the jet.

This seems to be a VM22 phenomenon (though I have seen it a couple of times in other carbs) and I don't know why it happens. You won't see it unless you look at the jet in a glass of petrol. The only way to shift it is with a very fine bristle.

 

[RETROHOWLA]

Hampshirehog, you really are an encyclopedia of the gs arnt you.
This may well be the problem then, although last year when i sonic cleaned these carbs i did 'rod' every jet and orafice through with varying gauges of wire to ensure none had a resin build up reducing thier size.
I wouldnt of thought i have many new deposits in such a short time but i may not have totally removed an old deposit.

As the bike is running and riding pretty good now i will prob leave it unless it starts to cause an issue with stalling etc as ive spent way more hours on his old tool and should have been spending them on the Gs1000 project thats been very slow going for this very reason!

One last thing, a 77 Gs550, what oil would you be running it on?
Haynes manual says 20w50?
Oil cap says 10w40?
And and for api spec?

I personally run the older high mileage stuff on a semi 20w50 but am curious as to what you guys run?

 

[hampshirehog]

You'll start a fight asking about which oil!

I put GTX in all of my bikes and have done for years. There's quite a discussion about the lower zinc levels they use in the mix now and some will suggest using diesel motor oil (higher zinc levels); in which case I would use Castrol GTX Diesel.

Having said that, on some old mutts I've owned I've just chucked in Wilkinsons own brand 10/40 or 20/50 (cheap stuff) and never had any problems. My golden rule - if it uses oil put in cheap stuff.

 

[RETROHOWLA]

Thats been my moto for years too, the oil burners get cheapo 20w50, this 550 is a little smokey so cheapo she will get

 

[bwringer]

Well a carb sync done and it idles a bit better but still seems a bit off on pot 1?

It starts on the button though and ticks over without too much complaint so i think im going to put it down to 70.000mile engine and carbs that just arnt going to perform like new anymore!

Nonsense -- there's no reason old carbs shouldn't perform better than new!

I'd run the bike for several hundred miles and then check compression.

 

[RETROHOWLA]

The fact that the owner cant afford to buy rebuild kits for the carbs makes me think they will be worn and not performing like new.

If i were able to rebuild them properly with new components im sure they would perform like new

 

[Billy Ricks]

New o-rings and a good cleaning will usually work wonders.