DoctorMotorcycle's Turbo Kit Development for 86-03 Sportster 1200's

[DrMotorcycle]

Revision 4 is done and the bike is up and running again.

A lot of thought went into this; I spent a lot of time reading comments and getting feedback from damn near every corner of the internet, from forums, Facebook, YouTube etc. I knew based off what I read that people didn't like the fact that the air filter was so close to the rider, so the first order of business was to move the setup forward. Additionally, I wanted to at minimum double the plenum volume, while also making sure that the intake ports are still the lowest part of the Coldside, which was tricky.

Not wanting to introduce a bunch of additional bends into the system, I decided to rotate the compressor housing 90*, so it now faces the ground. This allowed me to increase the length of the pipe leading to the compressor housing by 8". The plenum volume has gone from 200cc to 800cc. I switched to a Sifton intake manifold which also has noticeably more volume on the inside than the stocker (probably about 100cc, just a guess through).

As far as driveability goes; On Revision 3, the previous setup, there was a leak at the connection between the turbo/coldside pipe, and it was large enough that it would drip a drop of gas every now and then. Knowing that I was going to change the setup anyway, I just put a richer pilot jet in the bike until I could get around to fixing the leak. AFR's were high 15's low 16's during cruise, which is obviously too lean. I had to also open up the Thunderjet a full turn and a half to get the AFR's at WOT back down to 11.2-11.4.

I figured that it was the only leak, but I was wrong. As I was pulling off the old setup and prepping for Rev 4 fabrication, I pulled off the intake manifold and went to remove the hobbs switch (which was tapped/screwed into the intake manifold via NPT threads), and it wasn't even finger tight! It was literally 1/4 turn from just straight up flopping out. Solid mount vibrations strike again!

Here's the reason for me explaining this; you'd expect to see the AFR's at cruise come down considerably after fixing the vacuum leaks (they did, down to 13.8-14.2, 2 full points) in addition to having to back off the Thunderjet (main jet) the 1.5 turns that I made previously. However, at Wide open throttle and on only 6PSI, I had to OPEN the thunderjet another full turn. The jury is still out on how much power it picked up, but I will say that this is the strongest the bike has ever felt on this low of a boost setting, and that's while it's 110 degrees out!

Cold start seems to be the same, throttle response off idle has dulled slightly but as of right now I'm very happy with how this has come together. So much more legroom, more power, everything is really starting to come together now. Just need to add a small heatshield and here on out, Revision 4 is probably going to be the final revision. Test and Tune begins tomorrow, see you soon!

-Jimmy

[cycowrencher]

Have you done a Dyno pull yet?


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[DrMotorcycle]

Originally Posted by cycowrencher

Have you done a Dyno pull yet?


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Negative, still some changes I want to make before doing that. Also probably going to wait until it's not 110+ degrees here in Az as well, doesn't seem like the greatest time for dyno pulls, ya know?

[DrMotorcycle]

Update - Bike is running pretty good now on 9PSI, it's just so scorching hot that it seems unwise to raise the boost any higher than it currently is. Also, during Rev 4 fabrication, my Argon tanks were getting low, meaning that I could either slightly modify the current header, or get both of my tanks filled and do it the way I really wanted to (primaries away from the intake pipe reducing heat, 2.25" collector instead of 1.75" collector). Decided to take the easy way out, now I'm regretting it. Looks like there's going to be a revision 5 after all.

Without sounding too much like I'm trying to pat myself on the back; I'm giving up a lot of $ here in terms of lost revenue to keep testing and improving. Between YouTube, Facebook and Instagram, I've Have had about a dozen people reach out that are in the "I'm ready to buy right now" camp that I've turned down, solely because I'm not yet satisfied with where it's at. Thought Rev 4 was going to do it, now I'm thinking Rev 5 is the Ticket.

See you soon

[Medyo Bastos]

your build looks great! Let me know if you’d be interested in fabricating pieces for a n early 900 ironhead. I have a b-25 and hsr-42 that should work.


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[DrMotorcycle]

Originally Posted by Medyo Bastos

your build looks great! Let me know if you’d be interested in fabricating pieces for a n early 900 ironhead. I have a b-25 and hsr-42 that should work.


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PM sent.

[DrMotorcycle]

Originally Posted by Medyo Bastos

your build looks great! Let me know if you’d be interested in fabricating pieces for a n early 900 ironhead. I have a b-25 and hsr-42 that should work.


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Your inbox is full, I can fabricate a setup for you if I have the bike in my home shop here in AZ.

-Jimmy

[Medyo Bastos]

im not sure why Tapatalk says my inbox is full. I literally have 3 messages in there. I’m not able to send you a message either


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[IronHeadRon]

It's probably your sent messages, also conversations get collapsed. I'm guessing a premium membership solves it, otherwise email eachother or clean out all the box's (not just the inbox) if you wish to talk shop privately

Don't worry, I'll keep it on the low down your selling BLOW openly online. I just hope no one's bike overdoses (get my lame pun, huh huh, get it)

[DrMotorcycle]

Originally Posted by Medyo Bastos

im not sure why Tapatalk says my inbox is full. I literally have 3 messages in there. I’m not able to send you a message either


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My e-mail is doctormotorcycle@hotmail.com