![]() ![]() It screws into the carb body, with a nut locking it in place. The hot-start button is also on the left side of the carb. You'll want to scrape off the remnants so you can replace it with a new one later. ![]() There's a gasket behind the choke housing. This slide covers the starting jet, adding fuel to the mixture when the choke is engaged.Īfter removing the choke parts, remove the entire housing from the carburetor. There's another cable, return spring, and slide, just like the main throttle. On the PHM carburetors, the choke is basically a miniature secondary throttle. On the left side of the carb you'll find the choke assembly. The stock clip position on the PHM40SD was in the 3rd notch from the top. You can drop it down (higher notch) to lean out the mixture throughout the throttle range, or raise it up (lower notch) to make the mixture richer. The stock needle for PHM40SDs (on the 620) was a K51.Īlso note the clip position. You might want to note the number on the needle, in case you want to note the baseline specs of your carb setup. Remove it to get them out.Īt this time, you can inspect the needle for wear. The throttle cable and needle are retained with a brass screw. Note: there's a large rubber o-ring under the throttle cap you'll want to replace this with a new one from your gasket set later. This consists of the throttle cable, return spring, throttle slide, and the needle. Removing the top two screws exposes the throttle slide assembly. The throttle cable has a metal tube surrounding it I've already removed it in this picture.īefore we begin the rebuild, remember the float drain screw from 2 pictures back? Now would be a good time to loosen it, so you can drain fuel from the carb somewhere other than your work bench. On top of the carb, we see the throttle cable and the choke cable. Write this down you'll want to return them to their original positions during installation. Now would be a good time to see how many turns out your idle adjustment screws are. ![]() so, screw in to decrease fuel (lean mixture), screw out to increase fuel (rich mixture). Note, the idle mixture screw is a fuel screw. There's also another float chamber vent on the right side. On the right side, we have the fuel intake (and behind it the fuel filter), the idle speed adjuster, and the idle mixture screw. Note: not all carbs have the bottom float vent I have one that does and one that doesn't. Starting from driver's left, we have the hot start button, choke body, and some vents. Now, let's get familiar with your carburetor. #DELLORTO VHSB 38 MANUAL MANUAL#Here's a link to the PDF: DellOrto factory manual This is targeted more towards jet and needle selection, but it's handy to have. Wrench (adjustable, or several sizes to fit various pieces)Ħ. Flat-head screwdriver (one is necessary, 2 sizes is ideal)Ĥ. Second, you'll need the following tools and materials:ģ. You can consult the owner's manual on that, but it's pretty straightforward. Setting float height and float chamber installationįirst, I assume you have the carb off the bike. Inside the float chamber: needle/jet disassemblyĤ. The posts are pretty picture-heavy so I'll add links to the next/previous on each, in case you want to view them as single posts to speed up loading.ģ. I'll separate this into 6 parts and link to each from the first post (for those who want to skip ahead). Also, if anyone has suggestions on ways to improve this guide, please comment! I can do basic diagnosis, but if you're looking for advice on jetting/fine tuning, you should probably check the manual or ask an expert. I understand the basic theory and successfully took mine apart, cleaned it, and reinstalled it. I hope this helps somebody out there.ĭisclaimer: I am not an expert, and barely even a novice when it comes to carburetors. I wish I had done this about 15 years ago, then I could have attained Creeper-like status. like mine! Anyway, there's not much online info for these old-tech carbs, so I thought I'd share my experience rebuilding one. Specifically, the PHM38SD was used on the 400 LC4s, and the PHM40SD was used on the 620 LC4s. DellOrto PHM carbs were used on mid to late 90's KTMs, and probably some other euro bikes as well. ![]()
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