Author Topic: Racer Resurrection  (Read 70040 times)

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Offline bsracer

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Re: Racer Resurrection
« Reply #260 on: September 11, 2019, 12:04:13 PM »
I looked at my carb settings. I guess I tried some different things and didn't record them. I have the following:

4f15 needle
25 pilot
190 main
24/1 fuel mixture.

I had the clip in the bottom position and the mixture screw was farther out than I can remember. It was running rich last time out but I had also just reamed out a set of needle jets. My carbs are different than yours with a mix of jets from a few different carbs. I run 2.0 fuel valves as a replacement to the 1.5 stock ones that come in the carbs. I also swapped the float bowls with the external main jet type to some from a more modern 65cc mx bike with the large bottom hex screw access. I use the needle jets from these as well because they have the plastic shield around the main to keep down frothing. These carbs also have the neoprene black floats instead of the brass ones in the SR carbs. I've rattled more than a few of those apart.


p.s. we'll see how it goes at Barber

Offline al_pritchard

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Re: Racer Resurrection
« Reply #261 on: October 05, 2019, 09:52:54 AM »
I think you called it Brian. Unfortunately.

Tore down the top end to double check, and sure enough it's not to spec. Not even close. When I sent the cylinders off to Millennium for Nickel plating, we settled on a 0.002" clearance between piston and cylinder. I included the Wiseco pistons with the cylinders so they could be used for measuring the proper bore size. And everything came back in exceptional condition. Except as it turns out the cylinder bore size - are cylinders like people, expanding slightly over time?  ;D

Looks like what I actually have is 0.015" piston to cylinder clearance.
Bore: 1.9685"
Piston: 1.9535"

Rookie mistake, I ASSuMEd that the parts would be within speck. And it looks like they are not. I think my assumption was reinforced by what I thought was the correct ring gap. Such a learning curve...

Wiseco ring gap recommendations look like: Bore Size in inches x 0.005".

My ring gap with a feeler gage measures at 0.016". Looks like it should be closer to 0.009"

Time to jump on a call with Millennium.
Al Pritchard
Highlands, NJ

BS175 Racer



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