Author Topic: V7 Sport advance springs  (Read 272 times)

Offline czakky82

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V7 Sport advance springs
« on: July 01, 2022, 08:06:44 PM »
I’m putting a final spit shine on the drive train of my V7 sport and feel pretty confident in my jetting, etc.

I was just curious if anybody has tried the “low performance” advance springs in place of a “high performance” distributor setup?

I’m at least passingly educated in the dual point distributor variants. Just curious if it’s worth my hours worth of effort and $13 to try the faster advancing springs.

Offline jhem68

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Re: V7 Sport advance springs
« Reply #1 on: July 01, 2022, 10:35:34 PM »
Isn't there a difference in the distributors that require the stronger springs? My 850T has the same set up and the distributor's different from the 850T3 and newer that have a different advance curve.

For reference I'd suggest checking with Guzziology.

Wisconsin Rally would be a good time for you to showcase this project! And you might finally be the one who has an older bike than Jim Byrnes 850T.




Offline czakky82

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Re: V7 Sport advance springs
« Reply #2 on: July 02, 2022, 07:08:14 AM »
I’m pretty sure the distributors are the same. I have both in my possession and as far as I can measure they are the same.

I’m planning on making it to the WI rally. Likely Friday night, leave Saturday.

Offline jhem68

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Re: V7 Sport advance springs
« Reply #3 on: July 02, 2022, 02:33:41 PM »
Your stock distributor should be a Marelli part # S311A, stamped on the mounting flange pointing towards the center of the motor. Hard to see without removing the tank and looking in from the coils. If so that normally uses the "high performance" or stronger springs that slows the rate of advance in apparently an attempt to reduce the chance of pinging in Guzzi high performance models. The 850T3 and most subsequent models used the Marelli S311B model distributor with the weaker springs and had a different advance curve. And the initial advance is 2 degrees.
 Your V7 Sport has an initial advance of 13 degrees which compared to my 850T using the same distributor and has an initial advance of 8 degrees, is already starting from a relatively advanced position and combined with springs that could advance it too quickly in the lower RPMs possibly causing detonation.

Not saying you couldn't do the change, but I would refer to Guzziology chapter 6 under "Modifying big twin ignition advance curves". He supplies a very interesting graph.

John H

                                                                                                         


« Last Edit: July 02, 2022, 06:36:22 PM by jhem68 »

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Re: V7 Sport advance springs
« Reply #3 on: July 02, 2022, 02:33:41 PM »

Offline spmoto

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Re: V7 Sport advance springs
« Reply #4 on: July 02, 2022, 04:33:43 PM »
Don't do it! The distributors are different. I bought a T3 a few years back that gave me fits for the longest time until I discovered that the PO had apparently tried to hot rod it by swapping the springs. It wouldn't pull at all until you slowly worked it up to 4K rpm then it would rip.

Offline Tom H

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Re: V7 Sport advance springs
« Reply #5 on: July 02, 2022, 04:47:56 PM »
I’m putting a final spit shine on the drive train of my V7 sport and feel pretty confident in my jetting, etc.

I was just curious if anybody has tried the “low performance” advance springs in place of a “high performance” distributor setup?

I’m at least passingly educated in the dual point distributor variants. Just curious if it’s worth my hours worth of effort and $13 to try the faster advancing springs.

I tried the performance springs in a 1000 from a G5/SP. Low end power was not very good to say the least. Upper, 4000rpm and up it seemed fine. From what I remember from Guzziology, the heavy springs were intended for the LeMans series with the bigger valves and the like.

Tom
2004 Cali EV Touring
1972 Eldo
1970 Ambo V1000
1973 R75/5 SWB with Toaster
2007 HD Street Bob
1953 Triumph 6T (one day it will be on the road!)

Offline czakky82

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Re: V7 Sport advance springs
« Reply #6 on: July 03, 2022, 05:44:51 AM »
To clarify, the “low perf” springs actually advance faster than the “high performance” springs. In stock form on a stock bike, I.e: T3, G5, etc. they start with less advance and add timing faster. Like Jhem states, V7 and the like start advance at 13deg.

I’m probably going to leave this alone for now. Full advance is at 4K rpm and I don’t really use the range below that much. It does take some clutch and extra throttle to get going to avoid lugging in first from a stop.


 

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