Tuning issue and fuel issue

I am having a carb tuning issue on my bike that has been absolutely stumping me. like crazy. lots of long term issues that i can't seem to correct... at all. here is my run down of issues:

1. I keep getting fuel in my oil sump.
   1. petcock has been rebuilt and does not leak
   2. float needles/seats are brand new, fuel levels wet set perfectly to the low side of spec
   3. fuel will only got into my sump in 2 ways (i even added an emergency fuel switch)
      1. when i leave the petcock on prime and the bike is off and let it sit for a while
      2. when i ride the bike
2. I cant get my carbs to sync. (real YICS tool + Rick's homemade manometer)
   1. sync 3+4
   2. sync 1+2
   3. when i sync 1/2+3/4 it wont sync
      1. idle increases as i bring it in
      2. idle will not go down - even after idle screw is backed fully off of the adjustment plate.
   4. colortune is way rich with 1/2+3/4 out of sync and point where the bike is at the closest i can get and bike at proper idle
   5. colortune is white/orange flashing with sync in 1/2+3/4 and high idle. the color doesnt change until the pilot screw is completely closed.
   6. re-checked sync on 3+4 and now 4 is out slightly (how?)

I seem to be getting extra fuel leaking from the main itself when the bike is off, float levels are perfect. With the idle adjustment off the plate completely, the bike is running at 3500. opening the throttle or tightening the idle adjustment increases the RPM as expected. There are no air leaks either. When the bike runs, it is rich no matter what i do. I'm hypothesizing bad main needles/seats. I can't lower them any more. When I add air to the mix (i popped off a vacuum cap)... the bike dropped to idle, then stalled after a minute or so.

I also checked my carbs letting them on my bench rig (level) for a few hours and it felt dry around the jets. however, could the angle on the bike open up the needle enough to let fuel seep out the main?

1986 maxim xj700, Stock airbox, stock jetting, MAC 4 into 2 exhaust with straight pipes, Dyna coils only modifications.

Any other thoughts?

 

Leaking enrichment circuit somehow providing constant extra fuel.. ? No idea how it's getting into the oil however - if it's as you describe it doesn't seem possible.

 

well the leaking whatever. it is so rich, it's almost like there is unburnt fuel going through the cylinders sometimes, and it would seep down through the rings same as if the floats were bad.

 

I believe those are Mikuni carbs. Double check the fit of the seats and the o'rings to make sure they are a snug fit. The o'rings can leak with temperature change and flood your lower end.

 

They are hitachi hsc33

Float Needles and seats are brand new

 

Don't leave petcock on prime it should be on position IE with engine not running no fuel should run out of petcock only flow should be under vacuum . What are you using to synch carbs...I use a 4 vacuum gauge set up , have you pulled butter flys? If so it is possible one or more is not centered right( don't ask me how I know this ) I would pull carbs back synch screw out hold carbs up to light see if any light shows around plates..if it does you need to adjust plates. Use a buisness card under plates to do a bench synch you should be able to pull card out with just a little drag you should be close. Put carbs back on and see how it runs ..just my take.

 

I think you have two unrelated issues. First, I think your bench sync is off, e.i. the butterfly plates are open too much. When doing the bench sych make sure the idle adjustment screw is in the middle of its travel so you will have sufficient room to open or close them to get the proper idle speed.
Second, even though you have new seats and needle valves fuel has to be getting by them in order to get into the oil. I have an 85 XJ700N with the same carbs and it's easy to have an overflow when the correct setting is 1mm +/-1. I wet set my carbs after installing new seats and solid brass needle valves and left them hooked up to the fuel source for a couple of hours and then rechecked the settings and one was so high it was leaking fuel. I ended up setting my float levels at 2mm.

 

but are the fiber washers that go under the seats new?

 

They are copper washers I believe.

 

start with 1/2 then do 3/4
i think i asked before to pull the fuel line when you parked it. if you have the fuel line off you should see the gas go down and empty the clear fuel filter.
so now the petcock is out of the picture, if the gas goes down it's a float valve. if it's a float valve on one carb the gas has to go to the top of the bowl and into the throat, that carb cant work for awhile the next time it's started, look for a cold pipe

 

The copper washers go under the main jets.

 

xx3) Aftermarket Hitachi main fuel jetSPACER WASHER, round flat copper washer goes under the head of the main fuel jet. Perfectly replaces missing or bowed originals.

HCP887 Aftermarket Hitachi carbs main fuel jet SPACER WASHER, each:
$ 4.95

All I found in len's catalog.

Like I was saying before. The gas only goes down when it's parked if I put it on prime.

 

The fiber washers aren't in the catalog because they normally come in the carb rebuild kit. Trust me, the fiber washers go under the float valve seats to seal them when they are threaded to the float bowl inlet. If you don't remember putting them on the float needle seats, then that is where your leak is coming from. The reason that it only overflows on prime is that your petcock is working correctly. Even if the petcock was faulty, fuel can only get to the crankcase three ways;

1. Through a hole in the petcock vacuum diaphragm allowing fuel to run down the vacuum line.

2. Through a leaky float needle.

3. Through an ungasketed float needle seat via the threads for the seat.


#1 will allow fuel to enter the crankcase at all times.

#2 and #3 will only allow fuel into the crankcase when either the petcock is set to prime, or the petcock is leaking fuel due to faulty seals.

 

My float seats came with copper washers. Just saying...

 

I have copper washers on my float seats.

I did check my fuel filter last night (full), then this morning it was empty....

 

Copper fuel valve rings were original.....the replacements are red-colored fiber. All o' y'all are correct.

If you have your floats set on the low end of spec, that would contribute to floats that can leak.

 

There are many different versions of the HSC fuel seat WASHERS, because there are many different versions of the SEATS.......OEM, and a variety of different manufacturers/style of aftermarket seats.

The original Yamaha seats used a copper washer, about 1.00mm thick.

The aftermarket washers can be a red fiber material, clear plastic, or aluminum, and the thickness can vary from 0.48mm all the way up to 1.00mm thick.

You really should use the washer that comes with the seats that you purchase. Although some versions are very similar in initial thickness (i.e. un-crushed 0.48mm aluminum vs. 0.54mm red fiber washers), their thickness after install will vary.

Dave is correct, all the original Yamaha float valves used 1.00mm copper washers.

Tabaka45 is also correct, the fuel level settings on the HSC33 carbs is very finicky. Heck, tuning the HSC33's is an overall finicky process......


The HCP887 copper washers are for the main fuel jet, not the float valves.


All that being said, I don't have any real insights into jmilliken's issue(s).....it seems as there may be multiple issues involved, although if you are getting gas in the crankcase, then certainly the float valves are leaking, petcock on prime or not. I would recommend Tabaka45's advice and set the FUEL LEVELS as large as possible (he used 2mm), and use the clear-tube method of setting them, not any funky "float height" method of setting the floats.

 

One other thing: the above info regarding the seat washers (all except for the OEM Yamaha seat) can vary over time, i.e. the different aftermarket mfgs. have been known to change the material and/or thickness of their crush washers.....whether this is due to a part substitution or that they have switched to a different seat mfg. is unknown, but it happens.

Also, one supplier of the aftermarket float valve units provides incorrect assembles......they just won't work. Last we heard is that theu were using a 0.96mm thick aluminum washer with those sets.

 

i got a carby kit from taiwan boxes had yamaha symbols on them came with new float needles i installed them and carb started leaking i was going mad trying to set the float level motorcycle enginneer told me i got a dud a way to check for leaks is take the bottom bowls off turn the carbs upside down and suck on the fuel hose if theres any leaks you should hear from a perticular one if theres none you wont suck air ...you can get dud float needles

 

Pictures would be nice to see if we can pick anything out.

 

@chacal out of curiosity, the set I got from you looks like aluminum washers... Are you saying the washers that come with the set don't work?

 

I think it's the thickness of the washer that was incorrect, not the material.

 

Yea, so what's the proper washer?

 

No, some of our sets come with aluminum washers, too........what I'm indicating is that the sets that come with approx. 1mm thick aluminum washers are the ones that don't work properly (last time we looked, which was quite a while ago).

There is no "proper" size washer, the washers are different thicknesses depending on whose kit you are purchasing. Some float valves work properly, some don't, changing the thickness of the washer (from what is supplied with the kit) won't make any difference!

 

I don't know what's up. All the fuel levels are under spec. It was running nice last night (and tuned too) then this morning the fuel filter was empty and my (new) oil smells like gas.

I'm thinking about leaving the carbs on my rack at the angle they are on the bike, and seeing if I can see anything...

 

I have to ask is petcock set to ON or PRI? Think 550xj asked if you disconnected fuel line and tested petcock...easy enough fuel should flow on PRI but not in ON with no vacuum. If fuel is flowing it will put pressure on needle and could be leaking around one . Only trying to help you resolve this.

 

The petcock is fine.

 

if the petcock is good the most that could have leaked into the carbs or carb is one fuel lines worth. then i think it would have to partially fill the yics passage (maybe) and it only takes a teaspoon of gas to smell up the oil, not enough to worry about.

 

The sightglass will tell you how much fuel got into the crankcase.

 

Yea, it's just a little bit, but I want to FIX this issue. Fuel levels are about -4 mm, which is 3 under spec.

I did mic the washers under the needle seats and they are .96mm. I think I'm going to put the old copper washers back on... Then put it on my carb stand at the angle on the bike and see if I can find anything.

Out of curiosity... Would adding some food coloring to the gas hurt anything?

 

did you do polishing or rubbing compound on the needles and seats
are there any nicks or scratches on the float tang that could catch on the needle

 

Needles and seats are brand new

 

that's why you should mate the needle and seat. there could be a tiny mark in there you would need a microscope to see but gas will find it

 

https://archive.org/details/0542_Down_the_Gasoline_Trail_06_12_55_14

 

@Polock how does one mate the needle and seat? Should I take them on a date first, or just get down to business?

 

Booze and cigarettes are a tried-and-true method........

 

take the seat out, get a little of your polishing or rubbing compound in where the needle goes, put the needle in and push lightly and spin a lot is better than push hard and spin a few times.
after a short minute clean it up and you should see what you did and it should seal nice and tight. do it all over if you think it needs it, or just to see it get better.
those needles and seats should be considered a set now and kept together.
if you still have the rubber tip needles (me) just do the seat with a q-tip.