Over the winter. I made a bunch of changes to the bike. New coil, wires, Procom and finally a new speedometer with tach. I learned after adding the tach that my idle appears to be to high, around 1200-1300 RPM. However I cannot seem to lower the idle to the recommended 1000 +-50 without it being unstable. It wants to drop down to 800-900 then comes back up on it's own. And when I come to a stop it will drop down to almost 700 and stall.
Troubleshooting steps I took
-Checked for vacuum leaks.
-Put stock igniter back in.
-Put stock coil back in. According to the part number it wasn't for my bike.
-Upped the pilots from 42 to 45.
- Not a troubleshooting step but while trying to clean the carbs I busted the TPS and had to replace with "new" carbs.
-balanced the carbs.
What I have not done yet
-Check pickup sensor. Just changed the oil. Not wishing to waste it to check the sensor gap.
How do you know your new tacho is correct? If your bike was behaving itself, didn't seem to be racing at idle, and is running fine otherwise, set the f-ing idle speed back to 1200 rpms and ride on....
BTW, my first suspicion of an erratic idle would be a vacuum leak.
may very well be with that year Triumph the pick up sensor has an incorrect gap. with the cycle on the side stand you do not need to worry about the engine oil as with the left lean you lose no (very very little oil) but you will probably need a new gasket.
Wasn't able to get a gasket today. Decided to pull the cover and check it anyways. Fortunately I was able to do that without messing up the gasket.
Found the pickup was about 1mm, however it looked askew. not exactly centered of the lobe. Almost like the previous owner was trying to advance the timing. I reset it at .7. Need to top off the oil. Lost about a quart with the cover off. Waiting for my little one to get done with his movie so I can run to the part store for oil. LoL!
isnt it suppose to be .8? and I am surprised you lost that much oil. The 2 black wires will need to be sealed when you close it back up. Permatex black?
My understanding after searching the forum that it's .8 +- .2. It's a little tight on a .762 feeler gauge. Couldn't find my good sealant so I used a thin layer of some RTV silicone. I'm itchy to get it fired up and see the result.
Not sure that solved it. It was idling good in the driveway. Rode it up and down my rode cause I couldn't go to far and it seemed to do okay then started dropping in RPM again. Turned up the RPM to around 1100 and was a bit better. Opened up the mixture screws from 2.5 turns to 3. Haven't really tested it at that setting. Will try tomorrow.
Whoa, I missed that tidbit. I've never seen a case where 45 pilots were needed...most big bore folks have already swapped out the carbs to something more free flowing and that's the only application I can think of where one would even need to do that.
Over the winter. I made a bunch of changes to the bike. New coil, wires, Procom and finally a new speedometer with tach. I learned after adding the tach that my idle appears to be to high, around 1200-1300 RPM. However I cannot seem to lower the idle to the recommended 1000 +-50 without it being unstable. It wants to drop down to 800-900 then comes back up on it's own. And when I come to a stop it will drop down to almost 700 and stall.
Troubleshooting steps I took
-Checked for vacuum leaks.
-Put stock igniter back in.
-Put stock coil back in. According to the part number it wasn't for my bike.
-Upped the pilots from 42 to 45.
- Not a troubleshooting step but while trying to clean the carbs I busted the TPS and had to replace with "new" carbs.
-balanced the carbs.
What I have not done yet
-Check pickup sensor. Just changed the oil. Not wishing to waste it to check the sensor gap.
Replaced both. Went through them. Had around a 1000 miles on them according to the previous owner. Thing is they are doing the same thing the old carbs did and I went through those too.
It's hard to say. Needs to warm up for a bit before taking off the choke. But unstable idle seems to come on after awhile of running.
The bike has probably been this way before the changes cause I didn't have a tach to set the idle and just put it as low as I could go before the idle would drop an the bike would stall.
Current setup
42 pilot jets.
Removed shim on thruxton needles.
Sprayed carb cleaner through all the passage ways.
3 turns on the mixture screw.
Doesn't drop in idle after riding for awhile. Still cannot get it to idle below 1100. Best idle setting shows 1100 to 1250 on the tach. Popped a couple times in the carb.
Not really qualified to comment on carbed Bonnies, but that seems wrong to me. When you blip the throttle, do the revs take some time to come back down to idle?
They call that "throttle hang-up" usually caused by the mixture screws being too far out, specially with those 42 jets, the over-rich mixture causes the idle to drop, the user then adjusts the throttle stop screw to regain some idle. That causes the butterflies to end up being excessively opened uncovering the little progression or transfer ports just beyond the idle delivery port, right next to the butterfly edge.
The problem stems from the fact that the fuel that comes out of the transfer ports is supplied by the idle jets but it's not controlled by the mixture screw, the screw only regulates the fuel delivery out of the idle port.
Don't know how the Keikin CVK's are ,but here's a view of those ports on a Mikuni BST:
The keihin have those too. The idle was hanging up a bit.
I had the screws at 2 but was getting a lot of popping in the carbs. Get down to one and it really pops. Almost stalls. Took it up 4 to see the upper end but it didn't seem to affect the idle.
https://vimeo.com/164950233 video of the idle after my 10 minute ride from work. Idle was 100 so rpm higher when I parked it last night and I haven't touched the idle screw.
Forchetto, I gave a few revs and it doesn't seem to be hanging up.
yea and if you ever saw how low your oil pressure was much below 1200 rpm you would never want to set it that low. You don't need 45 pilots at all in your case 40s might be fine.
cold motor = lean mixture as it warms up mixture gets richer it needs to be set right with motor hot. Everyone gets hung up on how many turns out on fuel screws. Best idle will be had by turning each screw in and out till you get the highest idle speed. These motors are not all ways the same from one side to the other.
Still don't know. Most of the odd behavior is gone. Rpm isn't dropping off as it warms up. Most off the carb pop is gone. A lot of it went away after putting fresh fuel in the bike.
Still getting an occasional carb spit at idle and sometimes when giving a quick snap of the throttle off idle.
Idle mixture screws don't like anything under 2.5 turns. Idle gets rough. Best idle is at 3. Don't get much response after that.
Another update. Tried another round of leak checking and I think I found one on the inside by the carbs. Wasn't sure if it was the boot or the throttle shaft that was leaking. Was full tight on the clamps and yet the carbs were strangely loose and able to pull out. Found the boots inner diameter are slightly larger than the old ones. ????? Does the EFI's have bigger boots? Slapped the old ones on with new clamps. Had a couple misses when the idle is around 1000 but not like the big spits I was getting.
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