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Post by captincvmn on Dec 11, 2022 22:15:24 GMT -5
I’ve broken out the tiny fin before. I guess I wasn’t far off the mark.
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Post by captincvmn on Dec 30, 2022 16:19:26 GMT -5
Ugh!
I have GOT to spend some time trouble shooting and tuning my cylinder and carb. I miss riding so bad.
Idles fine, starts fine. Won’t rev past 8,000 and misfires/bogs above 1/2 throttle. Smoking lots when running also. Down to a 80 MJ and I’m using the needle from the 19mm carb that has a longer taper instead of the more blunt steeper w7 needle. Sorry, I don’t remember what it is. I have never ever pressure tested an engine. I suppose I should gather the necessary components to do so before I get scolded by the group.
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Post by 190mech on Dec 30, 2022 18:21:06 GMT -5
Sounds rich on the upper end,how is your air filter element?Have had them gradually clog with schmoo and cause a stupid rich mixture..
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Post by captincvmn on Dec 30, 2022 21:46:36 GMT -5
I’m running a “message board required” airbox. Filter is clean. Previously with the 19mm carb I ran a 78 MJ with a pod filter. Now with the 21mm I have a larger jet with the Airbox. Nervously weaning my way down.
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Post by captincvmn on Jan 4, 2023 21:11:22 GMT -5
Oh this MoFu is gonna kill me.
So I take it out on test rides, it goes “meh” and just starts to come up on pipe and ducking dies. I’m only 1/8mile in. Pull over, kick kick kick, WTF, choke, start. Ride away. Go almost back home, dies. Repeat process. Fuel hose is full of air with fuel at the bottom. Squeeze squeeze get air out so filter is full of fuel and hose too. Great now floor is covered. Wipe up and toss rag outside. Test ride. Same thing. Screw this air box. Something has to make a difference. Back to pod filter. Test ride. Go further and get higher into 9k rpm. Stupid Airbox, nope, dies again. Choke start ride back. Dies. Fuel flow issue maybe? Ok ride super mild. 6-7k and tickling 25mph. Rides fine. Little more, sputter. Let go and coast, gentle throttle, 20, fine. Crack throttle open, takes off……then starves. I’m going nuts here. Tomorrow night time allowing I’m gonna pull bowl plug and open petcock and time fuel drainage. Something has to give. I’m soon gonna abandon this manual petcock and go back to a vacuum one. Just doesn’t make sense. Aaaaaaaaaaaaaaahhhh! (Clumps of diminishing hair on floor of garage)
I honestly think it’s a fuel starvation issue. I mean I went from a 19-21mm carb and I’m sure jetting will be different, I’m assuming larger because velocity will be slightly slower past jets, I’m down to a 75 from a starting point of a 92 now. Still sucks.
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Post by oldgeek on Jan 5, 2023 0:02:26 GMT -5
..............I honestly think it’s a fuel starvation issue. I believe you are correct, sorta! It is simply an out of tune carb. I have been in the same boat as you many times. How can you tune a carb when you cant even ride it far makes a man go insane. I have made a needle change that turned a POS into a screamer. Jet changes that should have done nothing made all the difference. Slide changes that turned a pig off the line into a wheelie monster! (Ok not a monster, but I think you get what I am saying) I have cried myself to sleep at night over the Dellorto PHBG. You are not alone, but only you can get it done. Use the Force! I mean Choke, it can help you to find out if you are rich or lean. Divide it up find one throttle position that works a little, then work from there using the progression charts and needle charts to help. |
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Post by 90GTVert on Jan 5, 2023 6:24:09 GMT -5
People have their own preferences, but I like to focus only on the main jet and WOT first as long as it idles and runs well enough not to die on me otherwise. Main jet test runs in close succession will usually show a pattern and I think it's worth it to set the time aside to do them all at once whenever possible to eliminate variables. If it doesn't show any clear pattern, something else is up. Float height is a prime suspect if you just can't get it to run WOT and fuel flow seems sufficient. BTW, I don't see how a vacuum petcock will make tuning less of a headache. To me, it just makes one more thing to question.
I don't think it's your issue and I'm sure you know the difference, but observe symptoms as it dies to be sure it's just cutting out vs soft seizing. It's probably not gonna soft seize just as you get into the throttle. Still, if it cuts off and rolls free and kicks free immediately, it probably just died from lack of fuel or ignition issues. If you feel engine braking when it shuts off, then it could be hot and seizing. Sometimes a soft seize is OK to kick by the time you stop and get off and sometimes it will be tough to kick over till it cools more.
Hang in there. You've probably watched me struggle with tuning multiple times and I don't claim to be great at it but I've definitely done it a lot. When it's not going well, I find carb tuning/troubleshooting to be one of the most miserable experiences. When it really won't cooperate, sometime general condition checks can at least ease my mind that it's not some underlying issue fooling me... compression, leaks, spark and I'll pull the cylinder if I'm really lost in case there's a ring issue or something like that or at least check through the exhaust port to see if it's free.
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Post by captincvmn on Jan 5, 2023 7:49:50 GMT -5
I need to video what it’s doing. Has me stymied. Take off from stop, rpms come up, as WOT approaches it seems to pick up then falters and falls dead but still rotates. If I repeatedly open/close throttle it seems to keep running as if it has only idle fuel available, once I pull over it dies. Not suddenly but as if you just turned off the key and it spins to a stop.
I’m reasonably sure it’s not soft seize. I’ve had the engine just stop at rpms (lights go out, sudden death)
This loses power after 10 seconds on throttle but keeps running with zero power barely making any effort to go but then dies at curbside.
I’ll figure it out but it’s quite frustrating trying to locate the key.
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Post by captincvmn on Jan 7, 2023 15:23:53 GMT -5
 25m or less in 30 seconds through the jet change plug in the bottom of the bowl. Not encouraging at all. Next will be to check hose alone to see what flow I get there. |
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Post by 190mech on Jan 7, 2023 17:31:28 GMT -5
Fuel cap vent? Try the test again with the cap off..If it isnt better it's gotta be a restriction, got any funky in line fuel filters in the line?
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Post by captincvmn on Jan 7, 2023 17:39:41 GMT -5
Tried without the carb, just hose and got just shy of 100ml in 30 seconds.
Took carb off and messed with float again. Made them higher before shutting off flow. Retested with new bend. Between 75-100ml after bend operation through bowl plug. I’m good with that. Now I have gone on a ride, actually made it around the block a few times.
Had one starvation issue in the beginning but I think it may have been trapped air?
Bike rides better with choke on, gonna go up 2 numbers in the main jet and try again. Even with choke on it feels like the last 1/8 of throttle travel is flat. 7/8 throttle feels better than 8/8ths. Maybe raise up the needle some for more top fuel and if it’s worse I’ll go clip down from starting point.
At least I made it around the block this time.
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Post by captincvmn on Jan 7, 2023 19:22:09 GMT -5
Still feels flat on the top end. Clip adjustment made slow jet operation less even. Tomorrow I’ll go back to previous clip setting. It’ll do 50 on the road. Take off is kinda slow. Gotta get the clutch to engage higher.
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Post by captincvmn on Jan 8, 2023 20:12:49 GMT -5
Dropped the needle down to first notch. Cleaned up the rough low speed irregular heartbeat.
Still feels flat at WOT though. 3/4ish throttle has more umph than WO. Not sure why that is. Should I try and go back to the previous needle on a low clip setting? The previous needle (stock unit) had a more pronounced taper that would have supplied more fuel at WOT positions.
Seems to ride well and perform well. Doesn’t feel much different than the previous S6 cast iron cylinder or either of the Polini Corsa cylinders. Maybe I’ve gotten butt numb. Don’t really want to invest in a draggy just to compare sleeves. I’ve quite content to be able to cruise around at 50-55mph and pull a hill.
I do need to adjust my clutch somewhat so it’s in the power band at takeoff. Currently it leaves a stop sign at 6k and makes gentle progress to 8k when the party starts. Brent is the Torque Control clutch still the weapon of choice for good adjustability?
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Post by 90GTVert on Jan 9, 2023 0:49:37 GMT -5
Brent is the Torque Control clutch still the weapon of choice for good adjustability? It's definitely my choice. From what I've seen with my limited selection of aftermarket clutches; modified stock (stiff springs and lightened shoes) works well. The S6 Torque Control is even better and where I'm headed if modified stock isn't making me happy. |
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Post by Zino on Jan 9, 2023 1:45:14 GMT -5
Carb Tuning Can drive you Crazy
This is a race day trick to Test the main jet to see if how close to perfect it is for that days conditions
Go wide open then roll off the throttle 1/8 to 1/4 a few times .
This will temporarily richen you up
If your Rpms pick up or you feel more umph you are Lean on the main Go up a jet .
If your Rpms Drop immediately you are rich enough .
As far as needle after i have the main dialed in I take the needle position that is most responsive if 2 positions feel close I take the richer one .
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