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missing RPMs
#3379 02/07/2005 11:10 AM
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I have developed another problem that has me stumped...@ 3800-4200 rpms my right cylinder quits firing regularly. Everything is fine above or below that range. Plugs check OK. I think it may be carb related, but I need some input. Does this have anything to do w/ carb sync or vacuum leak?

bewildered again, TM


miles & miles of Texas... TM
Re: missing RPMs
mouse #3380 02/07/2005 4:18 PM
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That's about where the carb first starts running on the main jet and slide needle. My first guess would be that you need to get a can of carb cleaner and spray the daylights out of the needle and jet. If it doesn't fix the problem, it might be a good idea to shim your needles up or maybe change to the Thunderbird Sport or Thruxton needles.

Last edited by Greybeard; 02/07/2005 4:19 PM.

Let's hope there's intelligent life somewhere in space 'cause it's buggar all down here. -- Monte Python
Re: missing RPMs
Greybeard #3381 02/07/2005 5:35 PM
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Well, I've tried everything else BUT that. I thought I had cleaned the carbs real good when I removed the Freak and the 160 mains (never did get that set-up dialed in). I know those who have removed the airbox have been pleased with the performance gains onb the dyno, but I really couldn't tell that much "seat of the pants difference". I also had a lot of trouble getting the K&N filters to stay tightly attached to the carbs. I do believe these CVK carbs work better all around w/ the airbox. At least I did until this new problem began.

here goes...thanks, TM


miles & miles of Texas... TM
Re: missing RPMs
mouse #3382 02/07/2005 6:37 PM
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Hey Ed,

I was reading the COG(Concours Owners Group) forum the other day and there were quite a few members extolling the virtues of using Techron, Seafoam, or Redline in the gas just prior to an oil change in order to clean the carbs. Is this a viable option instead of taking the carbs apart? Do you think it could help to produce clean running carbs if you do it on a regular basis?

Re: missing RPMs
mouse #3383 02/08/2005 3:39 PM
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You must be doin something wrong. The airbox elim. kit provides significant HP gains, along with better rideability,ie: performance in the powerband, (if setup right) the airbox is restrictive and the bike is setup from the factory very restrictive and lean to say the least. I gained 29% HP with simple air/exhaust mods and moding the carbs. Finally got rid of the CVKs (they are whimpy) and installed the CR IIs, now over 70hp at the wheel. So again something is wrong with your bike to begin with if you noticed no significant gains, etc. Could be a variety of issues, too many for me to speculate. Have you checked your plugs/floats/coils/wiring connects/battery output/carb needles & jets/petcock/ virtually all fuel + electrical systems. May have to do a process of elimination or find a good Triumph mechanic that will understand your basic problem. GOOD LUCK, but again, yur bike should show noticeable performance gains with airbox elim + pipes and rejetting. PERIOD!

Re: missing RPMs
GUSSER #3384 02/08/2005 4:18 PM
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Gusser: Don't get me wrong, there was a difference w/ the Freak set-up, but since I don't hot-rod much anymore I'm looking for smooth consistent power. Finding a good Triumph mechanic in my area is the real trick. I asked the guys @ RPM in Dallas about my problem & they pretty much scratched their heads. I know it's hard to diagnose a problem based on a description, but they're 140 miles away. I'll eventually figure it out..maybe some trash somewhere I haven't been. I really think these carbs are more than sufficient enough to get me what I want. Thanks anyhow.

TM


miles & miles of Texas... TM
Re: missing RPMs
SalMaglie #3385 02/08/2005 5:13 PM
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'magic in a can' ?

for what it's worth i've heard 100 mechanics in my life extol the virtues of 'Seafoam'. i even know a car lot that runs it through all their vehicles prior to tune & sale. supposedly does wonders for topend as well.

Re: missing RPMs
jeff2 #3386 02/08/2005 6:25 PM
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thanks for the info...will try...anything, TM


miles & miles of Texas... TM
Re: missing RPMs
jeff2 #3387 02/08/2005 7:42 PM
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Well I've seen a few pics of some nasty buildup around the valves, so I thought some preventive maintenace might be in order.

Take a look at this teardown:

Remove Cylinder Head

IIRC, that Bonneville didn't have that many miles on it. This pic shows just how bad the buildup can get in a short time.

Last edited by SalMaglie; 02/08/2005 7:59 PM.
Re: missing RPMs
SalMaglie #3388 02/08/2005 8:00 PM
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Anything that keeps the jets clean or gets them clean will help. Especially whe you nromally run the bike right around the speed when the slide just starts to open, the crud they put in gas to make the gvt happy will tend to collect in a little ring around the needle from the gas vaporising as it gets pulled up the jet. Well, that will happen any time you usually ride at about the same speed and under the same load most of the time, it's just more noticable if it is where the needle fits tighter in the jet just around the speed when the slide starts to move. This will give you a narrow lean spot that goes away when you are running a few RPM faster or slower. I had a friend with a TR3 that used to downshift and then upshift right away to get off the dead spot caused by this effect.


Let's hope there's intelligent life somewhere in space 'cause it's buggar all down here. -- Monte Python
Re: missing RPMs
Greybeard #3389 02/09/2005 3:49 PM
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"build-up on needles"...haven't heard that one yet, but it makes sense. Looks like I'll be doing carb surgery again.

thanks, TM


miles & miles of Texas... TM

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