Y cover on airbox

[Zeus36]

Per Sean,
I dug out the Y section for the airbox and put in 1/4" spacers. Guess what?
It runs BETTER!

Before I converted to COPs, the bike would want to die at idle when it got hot, so I bumped the idle to 1250. (figured it was the carbs not being synced - hadn't gotten the sync tool yet.)There was also a rough point at 7K RPM. After the COPs install it would idle fine (and start quicker)with no more rough point at 7K. So I set the idle down to 1000 RPM and synced the carbs. When I was having starter clutch issues a few weeks ago, I was also getting a flat spot cruising around 4K-4.5K. Crack the throttle to open the mains and it gets past the flat spot, so that kinda ruled out a plugged fuel filter.

Thursday night I did a temp fix with new bolts on the starter clutch. Still had the stumble at 4-5K.

Just put in the Y this afternoon and all is good!

Without the tank cover you may find better performance if you reinstall the "y" section of the airbox. You can add about 1/4" worth of spacers. Fully opened up like that with nothing to control wind flow doesn't usually allow them to run to their potential.

 

[one2dmax]

You're welcome.

 

[sdt354]

My bike pumped out some decent numbers with the Y jacked up and trimmed. A home made crankcase vent system and a few other little things. I've got to credit the Marks exhaust for most of it though. There was more hp left on the table, seeing as I was still a little rich.

 

[Zeus36]

Since the prior owner had put on a full Dale Walker exhaust, I figured he had done something with the carbs. I checked the needles and found them to be stock units. Haven't looked at the jets yet..
Interesting that any restriction on the intake side has a beneficial effect on how the engine runs. I thought max intake air flow was the way to go as the engine cylinders would fill to full capacity, but I guess it is more about the Bernoulli principle inside of the carb.

 

[Traumahawk]

Well amount of air plays a key, but its also the velocity of the incoming air as well.

 

[one2dmax]

Well amount of air plays a key, but its also the velocity of the incoming air as well.

And there you have it.

 

[Jacksbugs]

Is it worth it/ok to put spacers on the Y with everything stock on the bike ? (exhaust, filter, needles)

 

[DMAN999]

Is it worth it/ok to put spacers on the Y with everything stock on the bike ? (exhaust, filter, needles)

I wouldn't bother.
If you have stock jetting and exhaust there is nothing to be gained by shimming the Y.
Even with stock jetting, exhaust and a K$N filter I don't think you'd see any benefits from shimming the Y.

 

[blaxmax]

Is it worth it/ok to put spacers on the Y with everything stock on the bike ? (exhaust, filter, needles)

I tried it a week ago and not worth it at all. You can shorten your springs in your slides by 3 rows with twist ties and shim your needle for a little quicker response. Slides will lift quicker and also return quicker.
I slot my cam sprockets and redegree them. K&N filter with 157.5 mains.

 

[Traumahawk]

I wouldn't bother.
If you have stock jetting and exhaust there is nothing to be gained by shimming the Y.
Even with stock jetting, exhaust and a K$N filter I don't think you'd see any benefits from shimming the Y.

I had a kerker 4-1, and was running a little bit rich on the dyno. I took the y off on the dyno and picked up almost 2 hp. But like I said, I was running rich, so that helped lean me out a bit.

 

[Docwade]

What are you guys using as spacers? Just some 1/4" length fuel hose at the mounting points?

 

[blaxmax]

What are you guys using as spacers? Just some 1/4" length fuel hose at the mounting points?

I used washers.

 

[Zeus36]

What are you guys using as spacers? Just some 1/4" length fuel hose at the mounting points?

I had a plastic drawer of male cable end compression connectors with spare compression collars. The collars were a perfect fit as spacers. When we used to rebuild the J-85 jet engines, all the 12-point titanium fasteners got replaced, but I kept a stash of the used stuff. Those were polished and put in place for the Y fasteners. (I don't run a faux tank cover))

Fuel hose will compress, so use something less flexible. I have six feet of 1/4" copper tubing from an icemaker off an old fridge that almost got re-purposed. A bit of work cutting them to length with a tubing cutter - but it would have looked interesting. (but you won't see them if you run a tank cover) May find some other application for copper on the bike...

 

[VMAXXIMUM]

I had a kerker 4-1, and was running a little bit rich on the dyno. I took the y off on the dyno and picked up almost 2 hp. But like I said, I was running rich, so that helped lean me out a bit.

Eric I'm running stock headers with supertrap slip on's and my bike is running a little rich. I also have stock 152.5"s. Rather than go down a size or two, based on your experience do think shimming the air box will do the trick?

 

[Traumahawk]

Eric I'm running stock headers with supertrap slip on's and my bike is running a little rich. I also have stock 152.5"s. Rather than go down a size or two, based on your experience do think shimming the air box will do the trick?

Yep, it should help. How much, Its hard to quantify. You can also go to a K&N filter which flows better than stock. One thing that I did, was to trim the lip of the filter to match the opening of the airbox. I did that at the dyno. It didnt help with HP on the top end, but it did help thru the midrange. A couple of hp, and a couple of lbs of torque.

Here is an easy way to look at it. Anything done BEFORE the carbs...remove the Y, raise the Y, change the filter, etc, will lean you out. Anything done AFTER the carbs...changing the exhaust, better flowing mufflers....etc, will richen you up.