It's just not right....

Re5Guy

Re5Guy

New member
Location
New Zealand
Hello all, I have been trying to get my RGS Corsa to run properly since it's first start in 30? years last month. I cannot get it to run properly at low revs. It goes fine as the revs increase, but it feels very rough and unhappy down low. I strongly suspect the carbs.
I have read and checked many suggestions on this forum and tried anything that seemed related, but in short....
- valve clearances are correct
- carbs stripped, ultra sound cleaned and new everything installed and set to std spec. It is running std jets, 65 pilot and 118 mains.
- Float levels carefully checked and rechecked
- chokes are fully off
- needle valves seating properly
- no air leaks evident.
-DMC/32 ignition fitted and new plugs. They are black and sooty looking if it has been idling, but look much better after a quick blat round the block.
-it starts very easily

There is a big clue which I don't understand the significance of though and I thought I would ask here. Adjusting the air/fuel screws makes no difference at all to the engine idle. At 1.5 turns out it runs exactly the same as 3 turns or 1 turn for all three.
Hopefully this will mean something?

cheers,
Tony
 
Sounds to me you still have a blockage somewhere in the idle circuit of the carbs. As soon as you remove that, the engine will react to the air screws. Ultra-sonic cleaning doesn't shift everything... not by a long way! It's a start, but certainly not the end-all.

Disassemble the carbs, again, use an air line with as much oomph as you can muster and blow through every hole and orifice that you find. You should find that the idle screw and idle jet openings, the small intake hole at the carb throat (follow the passage leading to the idle jet in the casting) and the 2 tiny orifices in the mixing chamber floor above the idle jet and idle screw are all connected to another, some more some less, depending on the direction you blow. Once you have ascertained all these passages are open and connected, the idle circuit will work as intended. And once that works, you can continue with tuning the carbs.

piet
 
Thanks Piet, so if this is the problem, then by implication all three of the carbs must have a similar blockage? Whilst it is possible, I wonder how likely it is....?
Only one way to find out though.... :)
 
It is in fact very likely, but in reality it only takes one not working to fuck it up for all 3. Been there, seen it, got the t-shirt... more often than I care to remember!

Often turns out you don't even find the bit of crud that has frustrated you for so long, but suddenly, the carbs start working properly. I don't even start re-assembly before I make double-certain that all those passageways are clear.

piet
 
The rubber sealing surface on the choke plungers goes hard over time too, and won't seal off the choke fuel. Have you checked the under side of the plungers?
Are 65 pilots standard on these bikes? Very big.
 
I agree it sounds like blocked idle mixture circuit. The prob is, some material can end up forced further into passages with very small exits, so finding clever ways to blast in the 'opposite' direction to normal air or fuel flow can be effective. Assuming you've checked all three plugs for strong spark? The fact that it starts easily doesn't indicate electrical though.

65s seem pretty big to me as well. if the pilot jets are correct you'll have best running with mixture screws between 1 1/4 and 1 3/4 out. But you need to ensure those passages are clear.
 
There is somewhere a list of orifices with the carbs out that with carb cleaner you can spray down and dependent where the spray comes out you can ascertain where a blockage is - @Rob ? I think you sent this to me but I can’t find it
 
Sir Sidney Ruffdiamond said:
There is somewhere a list of orifices with the carbs out that with carb cleaner you can spray down and dependent where the spray comes out you can ascertain where a blockage is - @Rob ? I think you sent this to me but I can’t find it
Click to expand...
found it - slightly different from what i remember but thanks to Rob Bradbury

PILOT BLOCKAGES. The easy way to check the progression galleries with carbs built
and on the bike is remove pilot jets and mixture screws. Open the throttle. Use a
can of carb cleaner with extension tube fitted. Put the tube up the hole where the
pilot jet goes; cover the mixture screw hole with finger and squirt cleaner while
looking for a stream coming up into the venturi, just in front of the back edge of the
slide. Then put the tube in the mixture screw hole, cover the pilot jet hole with
finger and squirt cleaner whilst looking for a stream coming out between the slide
and the engine. Finally put the tube into the little air hole under the carb intake (not
the "middle" one - the other drilling) Squirt and look for cleaner in the venturi.
 
Lots of good info here, and the problem most likely is carb related from sitting idle for so long.
Are the carbs synched and what condition are the slides? Of course the plugs will foul from just idling, but do they clear up after riding it more- try a hotter plug and check the choke plungers as noted above. Did you check that the floats are intact and don't leak and I assume the bottom of the tank is clean, along with the spigot filters. Liqui Moly makes a fuel system cleaner that supposedly is very good.
 
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I would concurr that blocked pilot galleries cause these symptoms.

I used to trade jap bikes and it was very common to find bikes that had stood would not idle properly, sometimes only with choke out.

Not sure if it's possible on an RGS but pushing the carb cleaner straw up against the pilot gallery jet at the rear and forcing the cleaner in would sometime clear it. You'll see it spray out through the idle mixture orifice equally, if it's clear.

I've done this with bikes running on idle but I'm not suggesting you flood your motor and bend your conrods.
 

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Carb/brake cleaner or compressed air, all serve the same purpose. The more pressure that can be applied, the more chance you have of actually shifting whatever is causing the obstruction. Chemically dissolving anything can take several days or even weeks. Whatever solvent that is introduced has to reach the obstruction first to acually work. Those passages that go straight into the casting can be cleared with a thin strand of copper wire.

piet
 
Tippie said:
The rubber sealing surface on the choke plungers goes hard over time too, and won't seal off the choke fuel. Have you checked the under side of the plungers?
Are 65 pilots standard on these bikes? Very big.
Click to expand...
Yep 65 is standard. I haven't checked the plungers, but I will now...that makes sense. Thanks
 
piranha-bro2 said:
I agree it sounds like blocked idle mixture circuit. The prob is, some material can end up forced further into passages with very small exits, so finding clever ways to blast in the 'opposite' direction to normal air or fuel flow can be effective. Assuming you've checked all three plugs for strong spark? The fact that it starts easily doesn't indicate electrical though.

65s seem pretty big to me as well. if the pilot jets are correct you'll have best running with mixture screws between 1 1/4 and 1 3/4 out. But you need to ensure those passages are clear.
Click to expand...
Yep spark is lovely and strong
 
Sir Sidney Ruffdiamond said:
found it - slightly different from what i remember but thanks to Rob Bradbury

PILOT BLOCKAGES. The easy way to check the progression galleries with carbs built
and on the bike is remove pilot jets and mixture screws. Open the throttle. Use a
can of carb cleaner with extension tube fitted. Put the tube up the hole where the
pilot jet goes; cover the mixture screw hole with finger and squirt cleaner while
looking for a stream coming up into the venturi, just in front of the back edge of the
slide. Then put the tube in the mixture screw hole, cover the pilot jet hole with
finger and squirt cleaner whilst looking for a stream coming out between the slide
and the engine. Finally put the tube into the little air hole under the carb intake (not
the "middle" one - the other drilling) Squirt and look for cleaner in the venturi.
Click to expand...
That looks very useful, thanks for this
 
TeddyG said:
Lots of good info here, and the problem most likely is carb related from sitting idle for so long.
Are the carbs synched and what condition are the slides? Of course the plugs will foul from just idling, but do they clear up after riding it more- try a hotter plug and check the choke plungers as noted above. Did you check that the floats are intact and don't leak and I assume the bottom of the tank is clean, along with the spigot filters. Liqui Moly makes a fuel system cleaner that supposedly is very good.
Click to expand...
Carbs carefully synched and slides in excellent condition. Floats are good (I did replace one as it was dodgy). I spend many hours cleaning the tank out (main problem was dried up fuel in there) and new filters.
 
Thanks for all the helpful suggestions guys, really appreciate it.

I will attack the carbs again and report back. I'm just happy that they are easy to get in and out compared to some other bikes I have battled with in the past.

cheers
 
Two weeks ago, I got a job to transport a Skyteam Ace.

The buyer told me the bike was at a mechanics and only needed the tank put back on after having the tank inside cleaned.

So I arrive and the flustered mechanic was revving the tits off it, but wouldn't idle.

I said, thanks to our esteemed Ron, "I'm not a mechanic, but it sounds like the idle circuit is blocked"

Carb came off, and he cleared the pilot circuit with compressed air. It idled for about 5 seconds and died. The mechanic gave me a smartarsed smile and said, "you're right, you're not a mechanic" ...... I rang my customer and told him it wasn't running and I wasn't doing the job.

I pick up the bike, again this week, the customer told me the tank went on after being cleaned, but hadn't been flushed out properly and the crud was blocking the circuit. I hope the real mechanic is around when I pick it up!

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