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Reduce  Engine Surging
Improve Throttle Response
Reduce Engine Ping


HD 2007/2008 Engines

High Heat on 2007/08 HD engines

HD 2007/08 Performance Recommendations

Cool your exhaust temperature with the Wide Band O2 upgrade for 2007/08 HD

Harley Camshaft Specification Tables

HD Twin Cam Engine Builds
TC 128 HP 95 CID
TC 100HP Street Engine

The basics of Fuel Injection explained

Rammer Performance Air Cleaners
TC Performance Heads 100+HP

Pro Tuning on a Shade Tree Budget


XLH 883 to 1200 Upgrade
by Rick 'Rickko' Eliopoulos

Yost Power Tube Installation

The last article left off with me disassembling my engine down to the cases pulling the heads and cylinders and taking them off to the machine shop Tuesday. Since dropping them off I continued on with this new experience (God I hope this thing runs again!).

Thursday night (4/2/98) I decided to tackle the Yost Power Tube (YPT) installation. I thought I'd do it in the kitchen (since I live by myself and don't have someone to remind me not to do mechanical work where I make sandwiches etc. Even though there is such a thing as soap and water, some women just don't like the idea.) I pushed everything aside and made room for the carburetor., screw drivers, vice-grips, paper towels, electric drill, and a coffee cup to dump the gas into from the float bowl.

A long time back, Maurice wrote an article entitled Changing' Jets. I printed it back then and had it handy as I started this task. I also had the magazine article just published showing a pictorial step by step procedure for installing the YPT. One thing you can be sure of in doing after-market installations is, if you work from the manufacturers instructions, you won't be able to figure out what to do (One exception. S&S has the BEST manual on installing and tuning an S&S carburetor I've ever seen. That company is top-notch. From manuals to customer service, they are the best! IMO). Maurice's notes and the pictorial were invaluable aids to the project.

Tip: If you use Maurice's instructions, mine or the magazine article, be sure to read them completely once or twice so you are prepared for each step with the right tools and parts on hand.

OK, here goes,

  1. Remove the throttle cable plate by clamping the screw head going into the side of the carburetor body with vice-grips. A slight turn and it'll loosen. Unscrew it with normal Phillips screw driver.
  2. Unscrew the only other screw holding it on attached to the top of the carburetor (black plastic spring cover).
  3. Unscrew the four Phillip screws holding the float bowl to the carburetor. body while holding it straight up.
  4. Gently lower the float bowl watching the float slowly tilt downward. The accelerator pump rod will come out of the rubber bellows on the side of the carburetor. No problem. Just insure you slip it back in on re-assembly.
  5. Dump the gas from the float bowl into that coffee cup (the one without your coffee in it), pat the rubber o-ring type gasket dry and put the float bowl aside.
  6. Gently turn the carburetor body over take a small crescent wrench or a screwdriver large enough to fit the entire slot of the main jet (brass piece screwed into carburetor body.) and remove the main jet and the brass tube its screwed into. If the jet is stock, it should have a very tiny number stamped into it like 160 or 165.
  7. Insert the new power tube and #180 or #185 jet included with the YPT kit and screw it down, but not to tight. I'd try the #180 first.
  8. Right next to the main jet set deeply into a narrow shaft is the slow jet. Replace it with a #45 if you have one. Also be careful to use the right size flat blade screwdriver so you don't damage the inside surface of the shaft.
  9. Carefully replace the float bowl insuring that the chrome accelerator pump rod goes back into the rubber bellows. Replace the four screws.
  10. Looking down at the top of the carburetor (black plastic cover), remove the remaining three screws. That cover has a large diameter spring under it so keep your thumb on it to hold it down as you remove the last screw. Then slowly lift it off the carburetor body.
  11. Remove the large spring.
  12. Carefully remove the rubber diaphragm that encircles the bore of the carburetor body.
  13. Remove the white plastic spider retainer.
  14. Remove the stock silver needle
  15. Pull the throttle slide out of the carburetor. Don't worry it can only go back in one way.
  16. Follow the instructions for drilling the 1/8" hole in the bottom of the throttle slide. Carefully clean out any metal shavings from the drilling process.
  17. Replace the slide
  18. Insert the new needle supplied in the YPT kit.
  19. Replace the spider retainer making sure you don't block the hole you just drilled out. The spider is keyed and should drop into the right position automatically.
  20. Carefully replace the rubber diaphragm. Don't damage this! Its not easy to replace. If it doesn't fit, wait 24 hours or until it completely dries out, it'll shrink into the correct shape and will be easier to replace.
  21. Replace the big spring.
  22. Replace the black cap or, if you've already got one, install the new chrome cap in its place. As Maurice said, this is the best time to do it!
  23. Replace the throttle cable plate and cinch up that one screw that holds it to the side of the carburetor body with the vice-grips.

Done! Replacing the carburetor onto the intake manifold will be covered when I describe the entire engine re-assembly process.

Oh yeah, not quite done. Don't forget to clean the kitchen counter before your SO comes home.

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Modification, Installation, Maintenance and Tuning Index  will help you find most of the information you want on one page.

How to get Professional Tuning Results at home
Testing the Innovate Motorsport LM-1 portable air fuel meter

Profession Tuning on a Shade Tree Budget

Veypor VR2 Data Logger and Instrument Panel
Video Installation and Demo
Purchase VR2

Engine Performance
How to Build a
TC96 2007 Engines
TC88 70HP Stage1  
TC95 128HP Stage 3
TC95 100HP Street
TC96 2007 Stage 1/2
EVO 64 HP Stage 1
EVO 74 HP Stage 2
EVO 82 HP Stage 3
EVO 95 HP Stage 3
883 to 1200 Upgrade
Shovelhead Modifications

New EFI for EVO and TC

Performance Gallery
Horsepower Gallery
Evolution 80
Twin Cam 88/95
Evolution Unlimited
Sportster Unlimited
Drag Strip Gallery
Land Speed Racing Gallery
CV Carburetor
Modifying the CV carb
Tuning a CV carb
Selecting a cam
Install a TC 88/95 cam
Install a Big Twin cam
Install Sportster cams

Camshaft Specifications
Twin Cam

Exhaust Systems
EVO Exhaust Testing
TC Exhaust Testing
Khrome Werks AR100 test
Making Drag Pipes Work

Shop Manual
Carburetor Troubleshooting
Finding Manifold Leaks
Cylinder Heads
Pistons and Cylinders
Belt Drive
Shop Manual Appendix
$20 Bike Lift
Plug Wires
Spark Plugs
Engine Tuning
Nitrous Oxide
Motor Oil
Stutter Box
General Information
WEB Links
Buy Books and Manuals
Performance Calculations
Estimate Horsepower
Estimate 1/4 Mile Time
Estimate Top Speed

Engine Displacement
Exhaust Length
Gear Ratios
Air Density

The Nightrider Diaries
The ramblings of a genius a, a madman and something in between.

Where is Sifton Cams?

Autocom Active-7 tested

Harley-Davidson EFI
-EFI basics explained
-EFI modifications explained

183 HP, 2 carbs, 2680cc

Copyright 1997-2006  Stephen Mullen, Oldsmar, FL -+-