V65C carb tuning |
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Jim
Senior Member Joined: 04 Oct 2015 Location: Rome Status: Offline Points: 111 |
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Posted: 04 Jan 2016 at 10:39 |
This is a long, sad story but I'll keep it as short as possible.
I've got a V65C with different pipes and conical air filters and it runs rich. So far I've: -> checked the compression which, if anything, is high but both sides are similar. -> checked the static and fully advanced timing with patience, dial gauge and a strobe. -> checked all the carb cables are free -> checked the tiny pilot airways are clear -> checked the float height -> changing the idle mixture had no effect on the colortune's yellow at tickover. At this point it was bluish above minimum. -> set the slide-stop adjuster screw to where it just touches the slide i.e. slide fully down and now, because of that?, I get yellow right through the range. I confess that the engine was cold during these tests but it starts without choke anyway. It's raining here in Italy and I want to keep it clean and it's too noisy to warm it up in the garage so I hope the temperature is not too much of an issue in basic setting up. I've run out of ideas. All help very much appreciated. Thanks in advance. |
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iceni
Senior Member Joined: 16 Sep 2014 Location: Colchester Status: Offline Points: 2480 |
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I'm having a similar problem with one of my British bikes. A thoughtful neighbour suggested that the solution may lie in a can of petrol and a box of matches, but I don't think I'll be adopting this particular remedy
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stuv65
Senior Member Joined: 29 May 2015 Location: Gloucestershire Status: Offline Points: 343 |
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Maybe I missed it, but what is the problem we're trying to fix?
First thing I would do rebuilding an old carb is replace the choke plungers as the rubber on the bottom goes hard and stops sealing the enrichment route. What are the carbs? PHBH30's? ta stuart
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Jim
Senior Member Joined: 04 Oct 2015 Location: Rome Status: Offline Points: 111 |
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Hi Stuart,
I'm trying, desperately, to set up the carbs. properly which are running rich and, yes, they are PHBH30s. As you suggested; I did order the choke plungers but they came without the rubbers which was useless. I won't mention the supplier. I read here that Matt Cooper at Eurocarb is good so I can try him. Before I order, is there anything else you'd suggest ordering? Jim. |
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johnno
Senior Member Joined: 19 Jul 2014 Location: loughborough uk Status: Offline Points: 5582 |
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is your bike running good ? the reason I ask is that my 650 runs a bit rich and I tried needles and re jetting and in the end gave up . Like you I don't need choke on start up unless well below freezing ,my bike as home made 2-1 system but does have original air box but my bike is well fast for a guzzi 650 ive even had it on track and it did its self proud ,mine as been running like this for over 4 years now . Eurocarbs are very good ,best of luck
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1100 sport corsa , Yam R1, guzzi 650tt rider
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Jim
Senior Member Joined: 04 Oct 2015 Location: Rome Status: Offline Points: 111 |
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Hold fire. On re-examination, the new plungers did have rubber in them so I'm going to put them in. Fingers crossed.
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stuv65
Senior Member Joined: 29 May 2015 Location: Gloucestershire Status: Offline Points: 343 |
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Might also want to check which notch the needle has the circlip fitted. I think the manual says 2nd notch but doesn't specify whether that's from the top or the bottom.
It's definitely counted down from the top and I think the second notch (but double check the manual). ta suart
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Jim
Senior Member Joined: 04 Oct 2015 Location: Rome Status: Offline Points: 111 |
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I put the new plungers in and reset the play in the cables (I've fitted a handlebar mounted choke lever with a splitter under the tank).
Now, at tickover, I can just about get a blue flame in the Colortune on the RHS but not quite blue on the LHS. From tickover to 1/2 throttle it's very yellow on both sides. Last time I opened it right up it was yellow all the way. I understand that tickover to 1/8 open is still the pilot mixture and then from 1/8 to 1/4 it's the slide cutaway and from 1/4 to 3/4 it's the throttle needle and finally from 3/4 to full it's the main jet size. The above are true but maybe there's something wrong which could cause a problem right through the range e.g. the choke plunger leaking or the fuel level in the bowl too high. I've checked these 2 though. Are there any other "global" things of this type I could check? What should I do next? Thanks again. |
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Jim
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Jim
Senior Member Joined: 04 Oct 2015 Location: Rome Status: Offline Points: 111 |
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Sorry - our last 2 messages crossed because I didn't refresh the page.
The owner's manual says 2nd slot on the needle. I did try the 1st too, which should be leaner, but with no effect. I think I've got something really obviously wrong but I've run out of ideas. Or maybe I've just managed to get a lot of little things wrong at the same time! Jim. |
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Mike H
Senior Member Joined: 21 May 2014 Location: East Anglia Status: Offline Points: 8733 |
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Throttle slides should be slightly open for idle, not fully blanked off, screw in the stop screws until there's about 1mm gap or so.
Then set idle mixture screws at 1.5 turns out from fully screwed in. Then check it again, it should be a bit too lean so engine doesn't like idling, but then screwing the mixture screws out should enable it to idle. Probably idles too fast now, so reduce the throttle stops as required. NOTE engine must be properly hot, I usually found that I have to reduce the throttle stops again after a few miles of actual riding because it wasn't properly warmed up when I first did it on the stand in the garden. If can't be done then carbs are screwed up somewhere; blocked or partially blocked jets, blocked or partially blocked air galleries, dirty air filter, floats wrong height or leaking or sticking, worn jets particularly needle jet and/or needle, if worn will let too much petrol through for the set throttle height. I note you've checked airways and jets are clear BUT I've had the experience where they LOOK clear but actually are STILL partially obstructed, usually by hard green or brown deposit which is the fall-out we get from modern unleaded petrol these days. Can be a nightmare to get rid of, last time a complete set of new jets was the only surefire cure. The other, choke plunger seals has been done. ^ |
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"Chicken nuggets don't dance on a Tuesday."
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Dave P.
Senior Member Joined: 12 Jan 2015 Location: Northants Status: Offline Points: 5573 |
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Are the springs which sit atop the choke plungers short or weakened therefore not holding the plungers down properly? I've seen an instance of this once.And how much play have you given the choke cables?should be 3 or 4 MM
Good luck |
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TO LIVE OUTSIDE THE LAW YOU MUST BE HONEST.
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telegraphroad
Senior Member Joined: 21 May 2014 Location: M11 J8 Status: Offline Points: 204 |
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First thing to do when setting up carbs is to make sure that the fuel is at the right level in the float chambers and that the needle valves are sealing properly and the floats are sound. I think there is a procedure for setting the float height in the literature so make sure you do that first. If you have a different fuel level RHS vs LHS then you will have different mixture even if the jets and all adjustments etc. are the same. Also, it's a while since I used a colourtune but I recall them being very sensitive to mixture setting and very difficult to see clearly. I wouldn't be surprised to see a slightly rich setting at idle on an older bike and a lean setting in the mid range. Fully open should be rich through the rev range, anything up to 12.5>13:1. Ride it for a bit then check the plugs.
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V50 Monza
VFR 800FI Herts / Essex border |
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Brian UK
Moderator Group Joined: 13 May 2014 Location: Surrey Status: Offline Points: 17641 |
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In my experience, when you find it running rich, and all the settings appear to be correct, check the needle jet, with the needle flopping about all the time it does wear oval, on my v50 you could actually see it. Changed the jets and all was much better, and it wouldn't cold start without help from the choke valve.
Did the same on the SPIII.
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Brian.
Better 5 minutes late in this world than years early in the next. |
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Jim
Senior Member Joined: 04 Oct 2015 Location: Rome Status: Offline Points: 111 |
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I had already done as you said. I screwed the throttle stops in 2 turns (from 6 turns out) so that should have lifted the slides about 1 mm I guess. The mixture screw was 1.5 turns out and I tried varying it too. Unfortunately, it certainly wasn't lean. The engine wasn't properly hot but that should only cause a pessimistically over-screwed in throttle stop screw.
So now I'm at the point where you say "carbs are screwed up somewhere" [:( -> blocked or partially blocked jets: the pilot jets are new and I can see through them fine. The main jets are 115 and old. I tried fitting new, standard 105 jets once but noticed a loss of power with the throttle wide open which is consistent with the 3/4 to full theory. I would have guessed that blocked jets would have made the mixture leaner but I confess not to know enough about the working of a carburetor. Do you think the old, 115 jets could be causing richness almost right through the range? -> blocked or partially blocked air galleries: 1. choke pass-through is not a problem here. 2. I've blown through all the pilot airways so they're not totally blocked anyway and stuck a pin up that tiny hole on the cylinder side and saw it come through with the needle valve screw removed. The holes that are straight I can see through, the others I can blow through. Anyway, I almost don't have a problem with the idle combustion setting. Could a blocked pilot airway affect the rest of the range too? -> dirty air filter: I've got inverse-cone filters fitted. I will clean them but they don't look obviously dirty. -> floats wrong height: I've checked them and they are 25mm as far as I can tell. The book says 23.5mm - 24.5mm so, if anything, they are set to keep the fuel level slightly low i.e. a leaner mixture. -> floats leaking: It shouldn't be possible for them to leak as I believe they are solid, black items. Do you know? They don't "dribble" when I get them out of the bowl but I might not get to them in time.I could dismantle them and put them in a bowl of petrol if necessary. As for sticking: -> floats sticking: Hard to tell. They seem free when dry and tipped upside down and don't stick. Again, I could lower them into a bowl of petrol and see whether it's possible to make them stick. -> fuel cut-off valve: do you know whether these could be causing the problem by not sealing? -> worn jets particularly needle jet and/or needle: Pilot jet is new anyway. Main jet, as mentioned above: replacing old 0.115mm with new 0.105mm jets didn't solve the yellow flame through the range problem. The needle is very probably worn. lowering it a notch didn't help though. -> Should I buy new needles? I'm not sure whether I should buy standard X8s, which is what it's got now, or whatever. There seems to be a huge range to choose from! I guess new 0.115mm jets would be a good idea too since they seemed to make it go alright. Shouldn't the needles have been replaced too when the jets were? I mean; is it OK to put in a bigger jet but leave the needle the same? -> throttle slides: new, standard as far as I know. I hope all this info. helps. -> bike history: After I changed the pipes and air filters it ran rough (not surprisingly!). I exhausted my tuning ideas and, for the first time in my life, took a bike to a mechanic. He kept it 18 months!!!! and I nearly didn't get it back. It ran OK for 1000 miles then went out of tune again. I've never managed to get it to run right again. I mention this because the engine has run OK since I changed the pipes and air filters with the carb. parts I have mentioned (except for those replaced with new versions of the same sizes etc.). Again I am struggling with these damned carbs. and losing my mind and too much of my life in the garage - I want to spend some more of it actually riding. So, all your help is very much appreciated! |
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Jim
Senior Member Joined: 04 Oct 2015 Location: Rome Status: Offline Points: 111 |
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This engine makes the plugs black and sooty in 5 minutes. I must be missing something HUGE
Thanks for all your posts. Johnno: your's is a bit rich mine has shedloads DaveP: the springs for the choke plungers are OK thanks because I can feel them as I tighten the screws down. Telegraphroad: I checked the levels as per manual (see above). I could definitely check / replace the needle valves (also see above). I can see the colortune better than expected so I'd recommend it. Brian: Needle and its jet: replace them, Yes. I'd like to know exactly what with though (see above) as I'm not convinced the combination I've got were ever legitimate |
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