When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
First time Harley owner here. Got a super cheap sportster from a guy that had it just laying around in a barn for 20+ years. He knew nothing about it and I wanted a project. Thus began my hellish project.
Once we got the motor open we found out it has been bored out to 1200cc. I put new pistons, rings and valves in and put it back together. The old intake was basically pooched and I made what I now think was a stupid decision and bought one of those cheap velocity stacks off of ebay. When I first put it together it ran but with some serious popping and lack of power. I then fried a starter and had to replace that. Once the starter was back in the bike refused to start.
Because it had already been running rough I bought a jet kit that said it would work for the big bore and aftermarket exhaust that is on it.
I rebuilt the carb (CV40 i believe) with the new needle, emulsion tube and pilot and main jets. I followed the advice that came with the kit to start large and work my way down. Over the last several nights I have now tried I believe every variation of Pilot Jet(45, 48, 50) and Main Jet(165, 180,185, 190, 195, 200, 205). Idle screw is set at 1.75 turns out.
At certain points the bike will start momentarily with the choke all the way out and then run for a bit and die but generally won't start up and I can't find any rhyme or reason for when it will start. Plugs are looking black basically every combination I try.
A friend mentioned that possibly the velocity stack is too short (see attached picture) and will never work. I have tried putting some extra screen and even some foam in it and nothing seems to work.
I am at a loss here. Before I go drop some cash on a new intake is there another problem that I might be having? Any help would be greatly appreciated.
Not an Ironhead so its a 1986 or newer. Should run fine without anything attached to the front of the carb.Check the filter in the fuel tank, and any filters in the fuel line
Tried it tonight with the original needle and emulsion tube. Started up with choke with both 165 and 205 but won't run without the choke on and the plugs are black. I am starting to think maybe we have some sort of air leak that might be the root cause now that I am back to original needles.
Stock 1200 jets should be 42 - 175
Stage 1 jet size varies, but typically 45 - 180
I'm not a carb guy but I would start with 45 and 180 you have.
Set the idle mixture screw to 2.5 to 3 turns out from lightly seated.
Check the float level.
Then I would look at the ignition, confirm plug gap, confirm spark, confirm timing.
Check your compression.
Are the push rods adjustable? You may need to readjust them.
I believe stock EVO Sportsters have different length non adjustable push rods for Intake and Exhaust.
longer pushrods have 3 stripes and the shorter have 1
Long=exhaust. Short=intake.
Of course with a unknown history you may not have stock pushrods or cams
Start with jet sizes #45 & #180. Those are the most common for a Stage 1 1200. The main jet (180) doesn't even come into play until 3/4 throttle, so you don't need to mess with it until your on the road.
Based on the bikes age:
Make sure the vacuum line to the backside of the petcock is good and not leaking.
A carb that age needs a complete rebuild which should include a complete strip down and I recommend soaking the carb body in Chem-Dip, available in gallon cans at most auto parts stores.
Intake manifold gaskets where the manifold connects to the heads should be replaced. Air leaks here will really mess things up.
Intake manifold gaskets where the manifold connects to the heads should be replaced. Air leaks here will really mess things up.
Yes, definitely change those manifold gaskets. It's really easy, you may have to remove the horn to get at the left side bolts. Those bolts are only 5-7 pound foot and likely easy to loosen (mine were), so don't fret like the exhaust nuts. Use some red high temp grease on the seals, make sure you don't mix up the flanges (one is marked R for rear cylinder IIRC) and you're good to go. A stubby Bondhus Allen wrench is great for the job, but I understand a common garbage disposal wrench works too! Who knew?
Just make sure you have the carb and AC aligned before final tighten of manifold bolts. See your FSM for this.
John
Last edited by John Harper; Sep 3, 2017 at 08:16 PM.
All of the above are very good recommendations. And cHarley and John H. are dead on with intake man. gasket leak tips. Such leaks are very common with these engines. Spraying/squirting plain water around the intakes will, of course, often indicate a vacuum leak by causing a rise or fall in eng. speed (if you can keep it running at a steady eng. speed while you, or a helper, spray around the intakes). Otherwise, you might want to replace the seals as a preventative maint. step regardless of whether they're leaking or not.
Another thing to check would be the carb rubber slide diaphragm. My machine ran erratically until I found several very small and difficult to see cracks or splits in the diaphragm. I'd also change out, or at least clean, those fouled plugs before you dig much deeper into it.
Note: I seen some very $erious 'Street Tracker' or 'Supermoto' type mods on that machine of yours (which is cool imo).
7 Surprising Harley-Davidson Products that Are Not Motorcycles
Slideshow: The bar-and-shield logo shows up on far more than motorcycles, some of the company's most unexpected products have nothing to do with riding.
Slideshow: From the troubled AMF years to modern misfires, these bikes earned reputations for reliability issues, questionable engineering, or disappointing performance.
Crazy Bunderbike Build Looks Amazing, But Is It Impossible to Ride?
Slideshow: The Swiss custom shop has taken a Harley Softail and stretched it into something so long and low that it looks closer to a rolling sculpture than a conventional motorcycle.
Engraved Rebellion: Inside Bundnerbike's Glam Rock II
Slideshow: A standard cruiser becomes an intricate metal canvas in the hands of a Swiss custom house known for pushing Harley-Davidson platforms far beyond their factory brief.
Slideshow: Harley-Davidson's challenges aren't abstract; they show up in dropping shipments, shrinking dealer traffic, and strategic decisions that aren't yet translating into growth.
Velocity Stack jet sizes
