Hi guys,
I have a 98 single carb vt600. This is the config that I actually got:
- Dragtron filter from a shovelhead, like this one: https://www.rustygaragecagliari.com/prodotto/filtro-aria-dragtron-air-cleaner-harley-davidson-per-carburatore-bendix-keihin-tillotson/ (I discovered afterwards from one of TJ's videos that these kind of filters mess up your carburation and they're not optimal)
- Silencer-free pipes
- Pilot jet from 45 to 47, the rest is stock
I feel like my carburation is messed up, in fact when I pulled out the sparkplugs I found that the front cylinder is running rich and the back one is running lean. I checked the intake manifold and I didn't find any leaks or cracks, the carb was overhauled one year ago with new gaskets, o rings and jet needle.
The bike doesn't run bad, other than hearing some bangs(not loudly and not frequently) when I decelerate.
The other day I tried to start the bike and it seemed like only the back cylinder was working. I pulled out the sparkplugs and the front ones were black and the back ones looked fine, as the image shows:
I cleaned all four sparkplugs, put them back in, and the both cylinders run, although I noticed some black smoke coming front the front cylinder pipe when I started it again and accellerated a little bit.
Again, I know I'm not running a very good configuration, especially with the air filter, but I don't have the original one and I would like to fix it with what I have, given that I plan to sell the bike. I also thought that maybe I should run a higher density foam inside the filter, because I think the main problem is the air that the carb takes in, and not the jets(maybe I'm wrong, or maybe it's both things).
Do you have any suggestion?
Thank you!
@Gabriele.Frs I would really investigate why the front cylinder is fouling before changing any jets or adding anything else to the equation Also if you are running open pipes and a pretty unrestricted intake your main jets should be much bigger I'd suggest you check out the Tuning FAQ page here - https://shoptjbc.com/community/brutalforums/topic/176621/tuning-your-carbureted-honda-shadow-everything-you-need-to-know
nNow with a single car bike one carb feeding two cylinders a carb adjustment should affect both cylinders Uneven mixture distribution is absolutely possible but one cylinder just dropping out kind of makes its ignition and mechanical condition likely suspects.
Now from your picture I can't tell if the foul plug is wet so I can't determine fuel wetness from like oil contamination my first move here would be get some fresh correctly specified plugs with the correct gap and check the front cylinder's ignition system both the plug caps the wires the coil connections and tests for spark performance Unplug one spark plug leave it in the boot set the threads on the fins of the bike and with the fuel off hit the start button just to just tap it, The point is to get the spark plug to fire so you can confirm it's getting a good fat blue spark.
Since this is a 1998 VT 600 if you have not refresh your ignition system I highly suggest you do that We do have an ignition kit on the website You're going to need to replace the wires and the boots They do go bad.
Also is your choke open while you're riding This is sometimes indicative of what happens when people leave their choke open and they ride. The choke on these bikes is not a true choke it is actually an enriching circuit it adds more fuel and a little bit more air for cold starts. Thus if the choke is left open you end up with a rich condition.
Next I would ensure that slide needle is actually lifting and the spring is working I highly recommend you also record the needle the main jet size pilot jet and mix screw setting before making any changes to your carburetor which I don't think you should make any changes at this point because we are trying to diagnose a bigger issue.
Next thing I would do is check for cylinder specific leaks looking for cracks is not enough here Manifold seals the clamps vacuum port caps that are leaking without any visible damage Need to check for all this stuff if the front cylinder keeps fouling spark plugs check your valve clearances and compare compression between cylinders Follow that up with a leak down test if compression is uneven Honda's diagnostic guidance here includes checking compression and ignition when investigating poor tuning so I know I'm not off.
Occasional mild deceleration pops with open pipes is not a reliable mixture test Check that your exhaust ports are sealed too make sure your exhaust is tighten down properly to spec and that you have fresh gaskets in there.
If you can tell me if the plug is dry and sooty or wet with gasoline smell or oily and greasy that distinction will actually help choose what you do next
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