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A vacuum leak is more evident at lower RPM, 4-5k is lower on a 1300 =
Spitfire engine. If changing the main jet to a leaner jet helped that =
might be because you were getting less air through the chokes because of =
a vacuum leak somewhere else and thus less air through the chokes meant =
a better air/fuel mix given the air leak bypassing the carbs and not =
going through the chokes. Easing the throttle gives the engine a chance =
to deal with the too fuel rich mixture while stomping on it shoots an =
over rich mixture into the engine and makes it stutter.
At higher RPMs this is not as evident a problem because the air leak is =
less of a factor when pulling lots of air through the carbs.
Did you check for leaks by spraying carb cleaner around the manifold? =20=
Bud Rolofson
Extreme Parts Racing (more than just a haircut)
71TR6 CC57365 (Good 6)
71 Spitfire MK IV Race Car #3
69 Spitfire MK 3 (back up FE engine/dinghy car)
93 Minnie Winnie Race Support Vehicle=20
77 Z-50A Hardly Davidson Honda Mini-Trail Bike (Triumph Pit Bike)
On Oct 16, 2016, at 9:14 PM, D V <explore8@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.
>=20
> 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.
>=20
> Re working the exhaust system as well as checking the float will be =
added to my winter maintenance.=20
>=20
> Sent from my iPhone
>=20
>> On Oct 16, 2016, at 2:21 PM, Barr, Scott <sbarr@McCarty-Law.com> =
wrote:
>>=20
>> Is it temporary? Just as you get on the gas out of a corner and then =
clears up as the revs rise?
>>=20
>> If so, do you have no oil in your dashpots or have you removed the =
dashpot pistons?
>>=20
>> Scott (B.)
>>=20
>>=20
>>=20
>>=20
>>=20
>> -------- Original message --------
>> From: D V <explore8@outlook.com>
>> Date: 10/16/16 12:53 AM (GMT-06:00)
>> To: Greg Blake <gblake58tr3@icloud.com>, fot@autox.team.net
>> Subject: Re: [Fot] Fwd: Stutter at 4K rpm
>>=20
>> 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.
>>=20
>> 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).
>>=20
>> It is missing and backfiring when I am full on the gas. I can prevent =
it by easing into the gas.
>>=20
>> I did notice some gas at my air cleaner to velocity stack connection. =
I wonder if it is a float issue?
>>=20
>>=20
>> Sent from my iPhone
>>=20
>> On Oct 15, 2016, at 7:35 PM, Greg Blake =
>>=20
>> 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.
>>=20
>> Sent from my iPhone
>>=20
>> On Oct 15, 2016, at 12:27 PM, D V =
>>=20
>>=20
>>=20
>> Sent from my iPhone
>>=20
>> Begin forwarded message:
>>=20
>> Date: October 15, 2016 at 10:30:51 AM CDT
>> Subject: Stutter at 4K rpm
>>=20
>> 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.
>>=20
>> 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.
>>=20
>> 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.
>>=20
>> It doesn't seem to be affected by turns and more related to full =
throttle vs easing into the gas.
>>=20
>> Backpressure from the loss of muffler or unrelated issues?
>>=20
>> 1300 spitfire with single Weber 40.
>>=20
>> Sent from my iPhone
>> _______________________________________________
>>=20
>> http://www.fot-racing.com
>>=20
>> 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
>>=20
>>=20
> _______________________________________________
> fot@autox.team.net
>=20
> http://www.fot-racing.com
>=20
> 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/levilevi@comcast.net
>=20
>=20
--Apple-Mail=_7334E4E7-23D6-4BB2-9F62-880EE9772E7D
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<html><head><meta http-equiv=3D"Content-Type" content=3D"text/html =
charset=3Dus-ascii"></head><body style=3D"word-wrap: break-word; =
-webkit-nbsp-mode: space; -webkit-line-break: after-white-space;">A =
vacuum leak is more evident at lower RPM, 4-5k is lower on a 1300 =
Spitfire engine. If changing the main jet to a leaner jet helped that =
might be because you were getting less air through the chokes because of =
a vacuum leak somewhere else and thus less air through the chokes meant =
a better air/fuel mix given the air leak bypassing the carbs and not =
going through the chokes. Easing the throttle gives the engine a chance =
to deal with the too fuel rich mixture while stomping on it shoots an =
over rich mixture into the engine and makes it =
stutter.<div><br></div><div>At higher RPMs this is not as evident a =
problem because the air leak is less of a factor when pulling lots of =
air through the carbs.<div><br></div><div>Did you check for leaks by =
spraying carb cleaner around the manifold? <br><div>
<span class=3D"Apple-style-span" style=3D"color: rgb(0, 0, 0); =
font-family: Helvetica; font-size: 18px; font-style: normal; =
font-variant: normal; font-weight: normal; letter-spacing: normal; =
line-height: normal; text-align: -webkit-auto; text-indent: 0px; =
text-transform: none; white-space: normal; word-spacing: 0px; =
-webkit-text-stroke-width: 0px; border-collapse: separate; orphans: 2; =
widows: 2; border-spacing: 0px; -webkit-text-decorations-in-effect: =
none;"><div style=3D"word-wrap: break-word; -webkit-nbsp-mode: space; =
-webkit-line-break: after-white-space;"><span class=3D"Apple-style-span" =
style=3D"orphans: 2; text-align: -webkit-auto; text-indent: 0px; widows: =
2; -webkit-text-decorations-in-effect: none;"><div style=3D"word-wrap: =
break-word; -webkit-nbsp-mode: space; -webkit-line-break: =
after-white-space;"><span class=3D"Apple-style-span" style=3D"orphans: =
2; text-align: -webkit-auto; text-indent: 0px; widows: 2; =
-webkit-text-decorations-in-effect: none;"><div style=3D"word-wrap: =
break-word; -webkit-nbsp-mode: space; -webkit-line-break: =
after-white-space;"><span class=3D"Apple-style-span" style=3D"orphans: =
2; text-align: -webkit-auto; text-indent: 0px; widows: 2; =
-webkit-text-decorations-in-effect: none;"><div style=3D"word-wrap: =
break-word; -webkit-nbsp-mode: space; -webkit-line-break: =
after-white-space;"><span class=3D"Apple-style-span" style=3D"orphans: =
2; text-align: -webkit-auto; text-indent: 0px; widows: 2; =
-webkit-text-decorations-in-effect: none;"><div style=3D"word-wrap: =
break-word; -webkit-nbsp-mode: space; -webkit-line-break: =
after-white-space;"><span class=3D"Apple-style-span" style=3D"orphans: =
2; text-align: -webkit-auto; text-indent: 0px; widows: 2; =
-webkit-text-decorations-in-effect: none;"><div style=3D"word-wrap: =
break-word; -webkit-nbsp-mode: space; -webkit-line-break: =
after-white-space;"><span class=3D"Apple-style-span" style=3D"orphans: =
2; text-indent: 0px; widows: 2; -webkit-text-decorations-in-effect: =
none;"><div style=3D"word-wrap: break-word; -webkit-nbsp-mode: space; =
-webkit-line-break: after-white-space;"><span class=3D"Apple-style-span" =
style=3D"orphans: 2; text-indent: 0px; widows: 2; =
-webkit-text-decorations-in-effect: none;"><div><div =
style=3D"border-collapse: separate; color: rgb(0, 0, 0); font-family: =
Helvetica; font-style: normal; font-variant: normal; font-weight: =
normal; letter-spacing: normal; line-height: normal; text-transform: =
none; white-space: normal; word-spacing: 0px; border-spacing: 0px; =
-webkit-text-stroke-width: 0px;"><br =
class=3D"Apple-interchange-newline">Bud Rolofson</div><div =
style=3D"border-collapse: separate; color: rgb(0, 0, 0); font-family: =
Helvetica; font-style: normal; font-variant: normal; font-weight: =
normal; letter-spacing: normal; line-height: normal; text-transform: =
none; white-space: normal; word-spacing: 0px; border-spacing: 0px; =
-webkit-text-stroke-width: 0px;"><br></div><div style=3D"border-collapse: =
separate; color: rgb(0, 0, 0); font-family: Helvetica; font-style: =
normal; font-variant: normal; font-weight: normal; letter-spacing: =
normal; line-height: normal; text-transform: none; white-space: normal; =
word-spacing: 0px; border-spacing: 0px; -webkit-text-stroke-width: =
0px;">Extreme Parts Racing (more than just a haircut)</div><div =
style=3D"border-collapse: separate; color: rgb(0, 0, 0); font-family: =
Helvetica; font-style: normal; font-variant: normal; font-weight: =
normal; letter-spacing: normal; line-height: normal; text-transform: =
none; white-space: normal; word-spacing: 0px; border-spacing: 0px; =
-webkit-text-stroke-width: 0px;"><br></div><div>71TR6 CC57365 (Good =
6)</div><div style=3D"border-collapse: separate; color: rgb(0, 0, 0); =
font-family: Helvetica; font-style: normal; font-variant: normal; =
font-weight: normal; letter-spacing: normal; line-height: normal; =
text-transform: none; white-space: normal; word-spacing: 0px; =
border-spacing: 0px; -webkit-text-stroke-width: 0px;">71 Spitfire MK IV =
Race Car #3</div><div style=3D"border-collapse: separate; color: rgb(0, =
0, 0); font-family: Helvetica; font-style: normal; font-variant: normal; =
font-weight: normal; letter-spacing: normal; line-height: normal; =
text-transform: none; white-space: normal; word-spacing: 0px; =
border-spacing: 0px; -webkit-text-stroke-width: 0px;">69 Spitfire MK 3 =
(back up FE engine/dinghy car)</div><div style=3D"border-collapse: =
separate; color: rgb(0, 0, 0); font-family: Helvetica; font-style: =
normal; font-variant: normal; font-weight: normal; letter-spacing: =
normal; line-height: normal; text-transform: none; white-space: normal; =
word-spacing: 0px; border-spacing: 0px; -webkit-text-stroke-width: =
0px;">93 Minnie Winnie Race Support Vehicle </div><div =
style=3D"border-collapse: separate; color: rgb(0, 0, 0); font-family: =
Helvetica; font-style: normal; font-variant: normal; font-weight: =
normal; letter-spacing: normal; line-height: normal; text-transform: =
none; white-space: normal; word-spacing: 0px; border-spacing: 0px; =
-webkit-text-stroke-width: 0px;">77 Z-50A Hardly Davidson Honda =
Mini-Trail Bike (Triumph Pit Bike)</div></div><div =
style=3D"border-collapse: separate; color: rgb(0, 0, 0); font-family: =
Helvetica; font-size: 12px; font-style: normal; font-variant: normal; =
font-weight: normal; letter-spacing: normal; line-height: normal; =
text-transform: none; white-space: normal; word-spacing: 0px; =
border-spacing: 0px; -webkit-text-stroke-width: 0px;"><br></div><div =
style=3D"border-collapse: separate; color: rgb(0, 0, 0); font-family: =
Helvetica; font-size: 12px; font-style: normal; font-variant: normal; =
font-weight: normal; letter-spacing: normal; line-height: normal; =
text-transform: none; white-space: normal; word-spacing: 0px; =
border-spacing: 0px; -webkit-text-stroke-width: =
0px;"><br></div></span><br =
class=3D"Apple-interchange-newline"></div></span><br =
class=3D"Apple-interchange-newline"></div></span><br =
class=3D"Apple-interchange-newline"></div></span><br =
class=3D"Apple-interchange-newline"></div></span><br =
class=3D"Apple-interchange-newline"></div></span><br =
class=3D"Apple-interchange-newline"></div></span><br =
class=3D"Apple-interchange-newline"></div></span><br =
class=3D"Apple-interchange-newline" style=3D"color: rgb(0, 0, 0); =
font-family: Helvetica; font-size: 18px; font-style: normal; =
font-variant: normal; font-weight: normal; letter-spacing: normal; =
line-height: normal; orphans: auto; text-align: start; text-indent: 0px; =
text-transform: none; white-space: normal; widows: auto; word-spacing: =
0px; -webkit-text-stroke-width: 0px;"><br =
class=3D"Apple-interchange-newline">
</div>
<br><div><div>On Oct 16, 2016, at 9:14 PM, D V <<a =
href=3D"mailto:explore8@outlook.com";>explore8@outlook.com</a>> =
wrote:</div><br class=3D"Apple-interchange-newline"><blockquote =
type=3D"cite">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.<br><br>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.<br><br>Re working the exhaust system as well =
as checking the float will be added to my winter maintenance. =
<br><br>Sent from my iPhone<br><br><blockquote type=3D"cite">On Oct 16, =
2016, at 2:21 PM, Barr, Scott <<a =
href=3D"mailto:sbarr@McCarty-Law.com";>sbarr@McCarty-Law.com</a>> =
wrote:<br><br>Is it temporary? Just as you get on the gas out of a =
corner and then clears up as the revs rise?<br><br>If so, do you have no =
oil in your dashpots or have you removed the dashpot =
pistons?<br><br>Scott (B.)<br><br><br><br><br><br>-------- Original =
message --------<br>From: D V <<a =
href=3D"mailto:explore8@outlook.com";>explore8@outlook.com</a>><br>Date:=
10/16/16 12:53 AM (GMT-06:00)<br>To: Greg Blake <<a =
href=3D"mailto:gblake58tr3@icloud.com";>gblake58tr3@icloud.com</a>>, =
<a href=3D"mailto:fot@autox.team.net";>fot@autox.team.net</a><br>Subject: =
Re: [Fot] Fwd: Stutter at 4K rpm<br><br>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.<br><br>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).<br><br>It is missing and backfiring when I am full on =
the gas. I can prevent it by easing into the gas.<br><br>I did notice =
some gas at my air cleaner to velocity stack connection. I wonder if it =
is a float issue?<br><br><br>Sent from my iPhone<br><br>On Oct 15, 2016, =
at 7:35 PM, Greg Blake <<a =
href=3D"mailto:gblake58tr3@icloud.com";>gblake58tr3@icloud.com</a><<a =
href=3D"mailto:gblake58tr3@icloud.com";>mailto:gblake58tr3@icloud.com</a>&g=
t;> wrote:<br><br>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.<br><br>Sent =
from my iPhone<br><br>On Oct 15, 2016, at 12:27 PM, D V <<a =
href=3D"mailto:explore8@outlook.com";>explore8@outlook.com</a><<a =
href=3D"mailto:explore8@outlook.com";>mailto:explore8@outlook.com</a>>&g=
t; wrote:<br><br><br><br>Sent from my iPhone<br><br>Begin forwarded =
message:<br><br>From: <<a =
href=3D"mailto:explore8@outlook.com";>explore8@outlook.com</a><<a =
href=3D"mailto:explore8@outlook.com";>mailto:explore8@outlook.com</a>>&g=
t;<br>Date: October 15, 2016 at 10:30:51 AM CDT<br>To: <<a =
href=3D"mailto:fot@autox.team.net";>fot@autox.team.net</a><<a =
href=3D"mailto:fot@autox.team.net";>mailto:fot@autox.team.net</a>>><b=
r>Subject: Stutter at 4K rpm<br><br>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.<br><br>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.<br><br>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.<br><br>It doesn't seem to be affected by =
turns and more related to full throttle vs easing into the =
gas.<br><br>Backpressure from the loss of muffler or unrelated =
issues?<br><br>1300 spitfire with single Weber 40.<br><br>Sent from my =
iPhone<br>_______________________________________________<br><a =
href=3D"mailto:fot@autox.team.net";>fot@autox.team.net</a><<a =
href=3D"mailto:fot@autox.team.net";>mailto:fot@autox.team.net</a>><br><b=
r><a =
href=3D"http://www.fot-racing.com";>http://www.fot-racing.com</a><br><br>Do=
nate: http://www.team.net/donate.html<br>Archive: =
http://www.team.net/forums<br>Unsubscribe/Manage: =
http://autox.team.net/mailman/options/fot/gblake58tr3@icloud.com<br><br><b=
r></blockquote>_______________________________________________<br><a =
href=3D"mailto:fot@autox.team.net";>fot@autox.team.net</a><br><br>http://ww=
w.fot-racing.com<br><br>Donate: =
http://www.team.net/forums<br>Unsubscribe/Manage: =
http://autox.team.net/mailman/options/fot/levilevi@comcast.net<br><br><br>=
</blockquote></div><br></div></div></body></html>=
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fot@autox.team.net
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