[Fot] Stutter at 4K rpm

[Duncan Charlton]

Derek,

One final thought.  Is the carb mounted with a Weber O-ring type mount with Thackeray (helical spring) washers and lock nuts?  On the TR motor the fuel can aerate due to vibrations, so if you have it hard-mounted perhaps there’s a harmonic vibration around 4000 rpm that could be causing this.  But — that seems unlikely since it only began after the off that damaged your exhaust.

Duncan Charlton
Elgin, Texas USA



> On Oct 16, 2016, at 10:14 PM, D V <explore8 at outlook.com> wrote:
> 
> Thanks again everyone. I checked the header to head and the exhaust to header connection and everything seemed tight. However I went 2 off hard at turn 4 this morning and my strap that was holding the exhaust is now mostly gone. I never figured out that 180 degree off camber turn all weekend.
> 
> To answer Scott's question, yes. I can brake downshift to 3rd in a turn. Full on the gas out of the turn and it stutters between 4-5k. If I do the same and ease into the gas I can most of the time keep it steady.
> 
> Re working the exhaust system as well as checking the float will be added to my winter maintenance. 
> 
> Sent from my iPhone
> 
>> On Oct 16, 2016, at 2:21 PM, Barr, Scott <sbarr at McCarty-Law.com> wrote:
>> 
>> Is it temporary?  Just as you get on the gas out of a corner and then clears up as the revs rise?
>> 
>> If so, do you have no oil in your dashpots or have you removed the dashpot pistons?
>> 
>> Scott (B.)
>> 
>> 
>> 
>> 
>> 
>> -------- Original message --------
>> From: D V <explore8 at outlook.com>
>> Date: 10/16/16 12:53 AM (GMT-06:00)
>> To: Greg Blake <gblake58tr3 at icloud.com>, fot at autox.team.net
>> Subject: Re: [Fot] Fwd: Stutter at 4K rpm
>> 
>> Thanks everyone for the replies. I will inspect the pipe to manifold and manifold to head to see if anything is loose or any leaks apparent in the morning.
>> 
>> I actually went down a main jet 145 to 140 and that seemed like it helped some but didn't clear up the issue (which is going leaner; opposite of what Greg said).
>> 
>> It is missing and backfiring when I am full on the gas. I can prevent it by easing into the gas.
>> 
>> I did notice some gas at my air cleaner to velocity stack connection. I wonder if it is a float issue?
>> 
>> 
>> Sent from my iPhone
>> 
>> On Oct 15, 2016, at 7:35 PM, Greg Blake <gblake58tr3 at icloud.com<mailto:gblake58tr3 at icloud.com>> wrote:
>> 
>> Don't know if my other email made it to you. Backfires on deceleration can be a lean condition. Have you checked your plugs?  Maybe something got "adjusted" with the bump.
>> 
>> Sent from my iPhone
>> 
>> On Oct 15, 2016, at 12:27 PM, D V <explore8 at outlook.com<mailto:explore8 at outlook.com>> wrote:
>> 
>> 
>> 
>> Sent from my iPhone
>> 
>> Begin forwarded message:
>> 
>> From: <explore8 at outlook.com<mailto:explore8 at outlook.com>>
>> Date: October 15, 2016 at 10:30:51 AM CDT
>> To: <fot at autox.team.net<mailto:fot at autox.team.net>>
>> Subject: Stutter at 4K rpm
>> 
>> Two races ago I went off track and bent my exhaust pipe enough to break the welded joint near the muffler. In the interest of time, I cut the exhaust at the muffler and secured the pipe to the frame.
>> 
>> At the last race, I noticed the car would backfire at deceleration which I am not surprised but I also noticed a stutter around 4-5k rpm.
>> 
>> At NOLA this weekend it is more pronounced and comes in when shifting hard from 3rd to 4th. After 5k, it clears up and pulls normally.
>> 
>> It doesn't seem to be affected by turns and more related to full throttle vs easing into the gas.
>> 
>> Backpressure from the loss of muffler or unrelated issues?
>> 
>> 1300 spitfire with single Weber 40.
>> 
>> Sent from my iPhone
>> _______________________________________________
>> fot at autox.team.net<mailto:fot at autox.team.net>
>> 
>> http://www.fot-racing.com
>> 
>> Donate: http://www.team.net/donate.html
>> Archive: http://www.team.net/archive
>> Forums: http://www.team.net/forums
>> Unsubscribe/Manage: http://autox.team.net/mailman/options/fot/gblake58tr3@icloud.com
>> 
>> 
> _______________________________________________
> fot at autox.team.net
> 
> http://www.fot-racing.com
> 
> Donate: http://www.team.net/donate.html
> Archive: http://www.team.net/archive
> Forums: http://www.team.net/forums
> Unsubscribe/Manage: http://autox.team.net/mailman/options/fot/duncan.charlton54@gmail.com
> 
>