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General Category => General Discussion => Topic started by: Thirtyaughtsix on July 21, 2018, 01:33:15 AM
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So I've been like this for awhile now, bike runs plenty fine but my mixture isn't anywhere near perfect as you can see. At the moment I'm thinking I either need to adjust my float height even more or get smaller jets. I don't recall the exact numbers as I don't have the book in front of me, but I remember the Haynes manual giving a measurement as to where my floats should sit and last I checked it's sitting at the maximum recommended lowest/leanest measurement. All the jets, floats, needles and chokes are brand new.
I can promise the chokes are NOT the issue.
The jets I replaced are all the same size as what comes standard on an 850T.
So my question is, do I set my float even lower, or do I opt for a smaller main jet? Is the main jet even the one I want for this issue? What size would I want? Please educate me :thumb:
(https://thumb.ibb.co/nK4OpJ/37217427_10216523387178037_3293873731415310336_n.jpg) (https://ibb.co/nK4OpJ)
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Could be weak spark too. I spent a long time tracing the cause of plug fouling on Triumph Bonneville and reduced jetting by 20% before I finally realized it was the spark plug wires. Remove plug cap and hold plug wire 10mm from head, should have a BRIGHT BLUE spark. Also , if you've had the heads off the cylinder head nuts may need to be retorqued.
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Most riding conditions are under the control of the pilot jet at the small throttle openings then the needle through the middle ranges. There is a lot of overlap. There has been a chart of this posted here not long ago. If it's your carbs you might start by lowering the needles or reducing the pilot.
That being said the previous advice on ignition should be heeded along with verification of timing, especially proper operation of the ignition advance.
Just remember this:
Most carb problems are ignition, most ignition problems are carbs.
Hunter
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Could be any of 4 parts of throttle settings. Mark your throttle w/tape, same w/housing. put a line on both at closed(take up slack). Now at wide open, then divide it in half w/mark, then 3/4 and another at 1/4 throttle. Now split the 1/4 to 1/8 and mark it.
Go out on those strait OH roads and hold the line at each setting for 2mi and do a plug chop on the side of the road. Start w/new gaped plugs. You should read a DelOrto book on it at Greg Benders site.
This is all good IF your ignition is correct.
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Will double check the timing then when I get a chance. Had it near perfect 9 months ago, but that was 9 months ago. Original dizzy
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The 850T and earlier VHB bikes use 142 main jets.
The 850T3 and latter VHB bikes use 120 main jets.
I've been using 130 main jets as a compromise, works fine.
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What are you using for an air filter? If too restrictive (or caked with filth) you'll run rich.
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Depending on the bike's mileage this one may or may not apply: 76 Convert had about 37K miles and I experienced the same thing after confirming timing (Dyna), replacing choke plungers, double checking needle position, float height, yada, yada, yada.
Turns out the Needle Jet was hogged out and somewhat egg shaped. Difference between old and new was clearly visible to the naked eye... New Needle Jets did the trick! :thumb:
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What are you using for an air filter? If too restrictive (or caked with filth) you'll run rich.
(https://thumb.ibb.co/enW4Gy/37206096_10216504105616010_3960508202566549504_n.jpg) (https://ibb.co/enW4Gy)
A pair of these guys here, brand new, maybe 700 miles on them. I still had this problem prior to putting any filters on there.
Depending on the bike's mileage this one may or may not apply: 76 Convert had about 37K miles and I experienced the same thing after confirming timing (Dyna), replacing choke plungers, double checking needle position, float height, yada, yada, yada.
Turns out the Needle Jet was hogged out and somewhat egg shaped. Difference between old and new was clearly visible to the naked eye... New Needle Jets did the trick! :thumb:
Mileage is 34k+ currently, both sides have new needle jets, prolly less than 2k miles on both of them.
Most riding conditions are under the control of the pilot jet at the small throttle openings then the needle through the middle ranges. There is a lot of overlap. There has been a chart of this posted here not long ago. If it's your carbs you might start by lowering the needles or reducing the pilot.
That being said the previous advice on ignition should be heeded along with verification of timing, especially proper operation of the ignition advance.
Just remember this:
Most carb problems are ignition, most ignition problems are carbs.
Hunter
What is the stock pilot size? What would the next size down be?
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What kind of exhaust?
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(https://thumb.ibb.co/enW4Gy/37206096_10216504105616010_3960508202566549504_n.jpg) (https://ibb.co/enW4Gy)
A pair of these guys here, brand new, maybe 700 miles on them. I still had this problem prior to putting any filters on there.
Any chance they are over oiled?
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What kind of exhaust?
Dunstall repliacs
Any chance they are over oiled?
I have no idea, how could I find out without pulling them apart?
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(https://thumb.ibb.co/enW4Gy/37206096_10216504105616010_3960508202566549504_n.jpg) (https://ibb.co/enW4Gy)
A pair of these guys here, brand new, maybe 700 miles on them. I still had this problem prior to putting any filters on there.
Mileage is 34k+ currently, both sides have new needle jets, prolly less than 2k miles on both of them.
What is the stock pilot size? What would the next size down be?
The jet sizes typically skip along by two or three. IDK the stock sizes. Have you tried the "plug chop" at different throttle settings on clean plugs to see which area might be out of whack?
If you want to dive in and get to changing something you'll need to see what jets you currently have and then get the next few leaner. If you want to start in the middle first see if dropping the needles in the slides helps at all. Swapping to leaner pilot jets will lean out the lower 1/3rd or so. If you have 48 now you would want to try 45 and 42.
Check Greg Benders site for the del Orto book. There is a method to the carburetor madness, once you get your head around it you can go straight to the problem.
You did check the ignition advance springs, right?
Hunter
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Question one. You're adamant that it's not the chokes, why? Please explain.
Question two, and it sounds stupid but someone did it today. Are you sure the main jet is in the accelerator pump and the pilot in the carb body. People get them backwards alot.
Question three. Have you inspected the oring on the choke jet where it goes into the bowl?
Question four. Does the idle respond when adjusting the air mixture screw?
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The jet sizes typically skip along by two or three. IDK the stock sizes. Have you tried the "plug chop" at different throttle settings on clean plugs to see which area might be out of whack?
If you want to dive in and get to changing something you'll need to see what jets you currently have and then get the next few leaner. If you want to start in the middle first see if dropping the needles in the slides helps at all. Swapping to leaner pilot jets will lean out the lower 1/3rd or so. If you have 48 now you would want to try 45 and 42.
Check Greg Benders site for the del Orto book. There is a method to the carburetor madness, once you get your head around it you can go straight to the problem.
You did check the ignition advance springs, right?
Hunter
I have not tried the plug chop thing, that's the whole letting one side run and pulling the cap to see how many times that side fires right? I remember the Haynes manual trying to explain the process to it but it was worded too archaic for me at the time. If I can find my fresh plugs I'll re-read that manual and try it out this morning.
I checked my pilots and they are size 50, whether or not that is stock is currently beyond me but that is definitely what the previous owner had at least, and what I had bought a new pair of. I'm thinking I should try some 47's maybe?
As far as the advance springs and weights go it's been the better part of a year now but I remember feeling confident about them, they were smooth and operated as they should according to Guzziology. I even remember making a thread about the springs themselves and which ones went where, or something along those lines. I've yet to dig into there again yet.
Question one. You're adamant that it's not the chokes, why? Please explain.
Question two, and it sounds stupid but someone did it today. Are you sure the main jet is in the accelerator pump and the pilot in the carb body. People get them backwards alot.
Question three. Have you inspected the oring on the choke jet where it goes into the bowl?
Question four. Does the idle respond when adjusting the air mixture screw?
The bike runs significantly different when either or both are pulled up/activated, spewing coal out the back etc.. They're also new so the o-rings are fresh.
Honestly I could see myself doing this! The 2 aren't different enough to where it would leave the bike inoperable? Pretty big gap between a 142 main and 50 pilot
Yes, again was last year but I vividly remember both o-rings falling where they should when the choke plungers were actuated.
Yes, played with these just 3 days ago. Went 5 ticks clockwise on both, bike began to struggle to idle, went 2 ticks back counterclockwise and it straightened out. Plugs still came out dark as midnight
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Could be any of 4 parts of throttle settings. Mark your throttle w/tape, same w/housing. put a line on both at closed(take up slack). Now at wide open, then divide it in half w/mark, then 3/4 and another at 1/4 throttle. Now split the 1/4 to 1/8 and mark it.
Go out on those strait OH roads and hold the line at each setting for 2mi and do a plug chop on the side of the road. Start w/new gaped plugs. You should read a DelOrto book on it at Greg Benders site.
This is all good IF your ignition is correct.
This is plug chop. What you described is idle speed & sync.
You need to go down the road after it's warmed up & check each quadrant of slide movement. Hold throttle steady on lines, then hit kill switch, pull over look at plugs.
50 is close to stock. Main should be no more than 150 for Dunstalls.
My 75T had 60 pilot/ 150 main/ needle all the way up. It ran sweet. It also had K&N(ovals) & Dunstalls