Quick jetting question
 

hey guys have a quick question on jetting my carbs, i followed the carb setup thread here over the weekend and jetted them accordingly

175 Front 178 Rear
#48 Pilot jets
No washers on Front and the stock washer on the rear needle
Fuel Screws at 2 1/4 Front and 2/12 Rear

Bike Runs and idles great pulls hard to about 7K Rpms where it starts to beak up and Cough just a bit before redline

wanted your opinion as where to go from there

Ape CCTs and Two Brothers High Mount Exhaust

thanks in advance

Couple of things to try......
Check your plugs (lean/rich) Should be a nice coffee color. Real light=lean, real dark/black=rich.
Do a less air test. Cover 1/4-1/2 of the intake on your air box with duct tape. Take it for a spin. If better, you're running lean. If worse, you're running rich. Always make adjustments 1 increment at a time.

You won't be able to use your spark plugs as a guide unless you do a plug chop at a certain rpm, using new plugs, then cut off the threaded portion so you can see the the color at the base of the insulator... Even then you will only be checking that particular rpm. There is far more info about plug chops that i am leaving out, but there are many helpful guides on the internet pertaining to that.

Covering half (or a portion) of the intake is a neat idea for testing. You can also use the fuel enrichener (some call it choke) knob. Hold the bike at the rpm that doesn't seem to be running right, and pull the knob out to richen it up. Once you know what that does you will be able to tell whether you need to add fuel or take it away.

More details would also be helpful such as: what altitude you are at, what air filter you have, whether you sync'd the carbs after fiddling with them (important to do this before changing anything else, or you may be chasing your tail), also any other mods done would be helpful.

James

stock filter and i'm in NE ohio so i'm about 1200 ft. ill see if i can get my hands on a carb tool i don't own one

Check for vacuum leaks and that the diaphragms are seated properly

done and done

"No washers on front and the stock washer on the rear needle."

Why did you elect for the above, the atitude you are riding?


Just wondering since I am going through the same process. I'm at sea level and started with adding wahsers per the famous post mentioned.
By the way, welcome back 8541 and thank you for sharing your carb knowledge!!!

its what 8541hawk had in his carb adjustment write up

If it pulls hard to 7K and then craps out I would bet the timing is out 180 degrees.

This happens when changing the CCTs if you screw up.

One of the reasons I don't believe in the "leave the front valve cover on" method when swapping CCTs

If you are unsure, it is the cams that end up 180 out.

Set the front cyl to the firing position, rotate 450 and check that the rear cam lobes are in the proper position.

ok ill check it out

BTW- (...for when you get that far) you can make a carb synch tool from a yardstick, some cable ties, about 6-8 feet of clear tubing, and some 2 stroke oil. There are also a few other versions of home made carb synch tools posted on the forum... hoping your issue sorts quickly. ;)

I'm not a fan of the yard stick type. I've had a couple and the problem is they can allow fluid to be sucked in. Last year i built a two bottle sync tool (obviously for twins only) out of two iced tea bottles. It works fantastic! No possible way the fluid can be sucked into the engine, very easy to use.

James

If I you put an aquarium regulator across the 2 sides you can make extreme imbalance manageable before any fluid gets sucked into the engine.

But favorites aside my only point is the OP doesn't need a costly tool that can be made... by more than 1 method...

:)

James

Timing is all set as well

No, you REMOVE the stock shim from the FRONT needle and ADD a 1mm shim, and the REAR needle you LEAVE the stock shim in place and ADD a 1mm shim (about 0.040" shim)

Your needles are too low at the moment

Hope this helps

:o

ohhhhhhhh ok it was worded kinda funny so i need a #4 stainless washer for both the carbs then correct?

Not sure abou the #4...we don't get washers sized that way over this side of the pond, but if a #4 washer is 1mm/40 thou thick then yes you need 2 of them...1 on the front needle without the stock shim in place, and 1 on the rear needle with the stock shim left in place.

:o

If you're having issues from 7,000 rpm on up, it is most likely the main jets - but even stock, they should be close enough for the bike to run well up to red line.


You could try going richer on the mains and see if it makes things better or worse (or try running it to redline with the choke partially on - safety first!) to see if that makes things better or worse.


I'm with 8541 hawk, though - potential vacuum leak or other issue may be a contributing factor.

Check the timing out first .

Are your velocity stacks in the correct locations? Short one in front, long one in back.

Yes timing is set and the stacks are in the right spot too, I picked up some #4 stainless washers I'll shim up the needles tomorrow like there supposed to be in hawks writeup and report back , thanks for everything so far guys it is much appreciated

I'm wagerin' two #4 washers are not going to transform this situation @ 7KRPM.. but hey it might work!

Check around the front of the airbox for obstructions.
Also do you have the plastic shield that goes over the front cyl under the carbs?

there's no obstructions, there cant be with how many times i've had those carbs off of there, and yes the hard plastic shield around the carbs?, yes that's still there

Did you mess around with the floats in the float bowls while dealing with your carbs? You could be running out of fuel.

Fuel starvation is a good thought. I was experiencing my engine falling totally flat and sometimes quitting at constant throttle around 5000 rpm. Disconcerting when surrounded by semis on the highway to say the least. Took my petcock apart and discovered diaphragm was torn in several places. Replaced it and am now good to go. No similar issues all the way up to near red line ever since. Might want to check yours and see.

:iagree:

No I've never messed with the floats, and I think 2 years ago I did replace the petcock diaphragm

OK guea shimed the needles up with the washers. The breakup now happens at 7k it coughs a bit them finishes reving to redline. Pulling the choke out makes it worse