Importance of details

[Spatt]

Working on a motor for a customer and was kind of disappointed in the initial pulls on the dyno.  I adjusted cam timing and I couldn't get the top end power I was expecting.  Pushed timing into the motor and still power was lower than expected.  I decided to pull the motor and had resided it would be a back up motor and to replace it with the identical motor on the floor.

During pulling the motor I noticed when pulling the throttle body assembly it had ported throttle bodies and had previously had a ported head on it so I just assumed the coupler that attaches the throttle bodies to the head had already been matched but had not.  It was totally my fault for not catching it and blended them to a trashed ported head and reassembled the bike.

I wont share final numbers but its healthy for an MA Dunlop on a stock FZ wheel and spec fuel.  The part that impressed me was the effect it had on power.  The path would look something like this >< going from a larger orifice to smaller orifice then to the ported head.  

Just putting it out there that details matter when working in a complex system such as a motorcycle.  

Just for those that aren't clear what boots I am referring to here is a photo of them I found online.

[blackout]

Thanks for sharing these details.  Glad you are on this forum helping the regular folks out. 

[Spatt]

I honestly wouldn’t have thought it would have been that big of any effect.  From 6-11k it was 5-9 hp

[Spatt]

2 hours ago, blackout said:

Thanks for sharing these details.  Glad you are on this forum helping the regular folks out. 

To be clear I’m just a dude in a barn.

[DewMan]

13 minutes ago, Spatt said:

To be clear I’m just a dude in a barn.

I'm sure I'd be jealous of your barn. 

[Hosleymoto]

I’m a little confused, so it had ported throttle bodies and a crappy ported head with stock boots? Or ported throttle body’s stock boots and stock head? 

[klx678]

Poor little fuel molecules were stumbling over the step now, weren't they. 

Now they're happy little fuel molecules!  

Edited June 25, 2020 by klx678

[sorkyah]

im a bit confused as well
was it just causing too much of a restriction on the boots? were the throttle bodies ported but not polished? 
was the head not port matched? 

[klx678]

Not positive I'm correct, but proper fitting would have a smooth blend from injector or carb throat through the manifold and into the port.  Sounds like that's what was forgotten, fitting the throats of the manifold and injectors for smooth flow.

Edited June 26, 2020 by klx678

[Spatt]

On 6/26/2020 at 1:56 AM, sorkyah said:

im a bit confused as well
was it just causing too much of a restriction on the boots? were the throttle bodies ported but not polished? 
was the head not port matched? 

correct the boot in the photo needs to be matched.