fuel shutoff, replumbing, & individual filters

[ratbyk]

Cone air filters

JCarlton, thank you for the confirmation on my assumption. Mike, the filters I have, had; "Taco" written on the box but who knows now days. They all may be manufactured by the same people and boxed to fill different venders orders.
Anyway, as I stated in my last post; I went out for a ride this am with no more changes to the carburetors. I had removed the "cone" filters and installed the rubber ram tubes from the original air box. Bike flashed right up no problem, backed off to half choke within 20 seconds, off choke alltogether within 45 seconds and went riding. In traffic etc. everything felt real srong. No hickups, burbles nothing. Worked just like it should. Headed out West Coast Rd. Once I got to a place I could let it out a bit without drawing the Mounties I started in 3rd gear at 2000rpm. I wrapped it all the way to 8000 with nothing out of the ordinary. It pulled very strongly, absolutely seamless all the way up. I shut it down at 8 grand ( thats fast enough fot a 24 1/2 year old engine.) I pulled the plugs and they were a nice tan colour. Just what I was looking for. Went home and swapped over to the "cones".
Did the same trip. Bike did not feel as crisp as on previous run but no missing, burbles etc. Now when I got to my test point again started in 3rd at 2000. Let it out, not as crisp or as strong as previous run. At 5800 the engine started to burble, by 6000 it started to break down and would not go over 6200. Just flattened right out and would not run beyond 6200 or smooth out. Pulled plugs. Solid sooty black. The only change I had made was to install the "cones"!
Well that confirmed my suspisions. As I made both of these runs, I travelled along beside the Straits of Juan de Fuca. The sun was shining and the water as calm as it could get. After 3 1/2 days of fiddling with Mikuni carburetors and the associated fuel system bits and pieces I said to myself; "I'M GOING FISHING!". Which I did. I believe I have my problem figured out. Just need to get out the exacto knife and do a little carving. Which I am about to do now. Will road test again in the am and report on latest findings.
Ken/Sooke
78E Ratbyk


Did.

[ratbyk]

Cone Filters

Ah the saga of these cone filters, will it never end?
Went out to the shop, pulled a "cone" off the bike. Took a WD 40 bottle and sprayed the carb air horn Took a piece of paper towel and pressed against carb air horn to make an immage of the air horn with all ports in place. Made a bit of a template from that. Felt pretty smug and smart. WRONG! First cut struck metal before passing through the shoulder. Looked closer, did a little pushing and prodding and the whole rubber intake port on the air filter came off to reveal a groove all the way around the collar that retains it into the metal end plate of the filter. Scrap one "cone" air filter! Better yet scrap all 4 "cone" air filters.
On checking things out further discovered that the inside measurment of the carb air horn is 50 mm. The inside measurment of this shoulder inside the filter is 41 mm.
SO! As the rpm goes up, the throttle slide rises further and further and smaller opening on the air filter starts to act like a choke. Up goes the vacuum in the venturi up goes the amount of fuel being drawn into the system until the air/fuel ratio starts to flood out the engine. (around 5800, I know)
Back to the original ram tubes (velocity stacks-whatever) I think the age old advise;"don't fix what is'nt broke" applies here.
End of story. I hope- anyway I'm sticking to it.
Ken?Sooke
78E Ratbyk.

[Mike Hart]

there's cones and there's cones...

Negative info is good info, thanks guys.

I got my Kustom Kones from cycle-recycle online, the instructions for ordering said to measure the carb diam and get that size or one size smaller. I ordered four 54mm filters, delivered to my door $41.80. They fit great, and have no restrictions inside.

Click fuel system parts in the left nav bar, then air filters. They list the 54mm ones as fitting GS750/850/1000/1100 '80-'86 * FJ1100/1200 * XS/XJ1100 '80-'82

Don't know why they don't have 78-79 listed....

item# EMGOPOD54

[Rick Wood]

Jetting

Mike,

Did you ever get your jetting right.

[Mike Hart]

Rick, I'm waiting on a set of 50 pilots I ordered almost a week ago... I'm hoping they come in soon so I can get it done. Will let this thread know for sure!

[Mr Jake]

jets and vacuum lines

I have two questions that are related to two different topics within this thread.

Question #1 For those of you that have found success in T-ing your fuel lines together and getting rid of the octopus, what have you done with the engine vaccum line that ran to the octopus? Is it important? I have an '80 SG.

Q#2 Another quirk of the '80s and '81s is that the stock main jets for the two middle cylinders were ten sizes larger (120) than the outer two cylinders (110). The only reason I can think of for this is that the middle two cylinders are going to run hotter than the outer two. For those of you with '80s and '81s that have changed out your main jets, do you keep the middle two running ten sizes larger or have you gone to one size across the board?

I have seen many guys writing that they are running one size or another but I never hear anyone claiming to run two different jet sizes.

[Mike Hart]

I just capped off the vacuum outlet that went to the octopus, that's all it was for. Got an automotive (was it 3/16ths?) one from NAPA that looked like it could take the heat better than the cheesy ones at the 'inferior' chain stores up here. It is important, in the sense that you don't want an open vacuum port, you need to plug it.

Jet sizes are in increments of 2.5mm, so from 110 to 120 is four 'sizes', 10mm bigger. I've heard of both, and since EPA considerations made Yamaha want to get things as lean as possible, perhaps when you jet up and are maybe a tad richer than factory you can go same size all across. I've seen the charts that give that 'different size' info, but also have heard from folks that their stock carbs had same size all across.

[Wayne]

Hey Ken,
Thanks for sharing your experience. I had a similar problem this weekend. I installed cone filters last week. Saturday was the first day I was able to ride. VERRRY hard to start, ran like crap, died at every redlight and knocked and pinged at higher rpms.
I am going to take a look at my cones today and see if Im having a similar prob. as you. I will probably just go back with the stock airbox as she ran really good before.

[ratbyk]

Cone Filters

Wayne, if you pull your plugs after it has acted up and they are black-black-black, then you have the same problem that I did. Look up inside the throat of the "cone" air filter for a large rubber shoulder. Mine were 41 mm across. The inside measurement for the 34 mm Mikuni air horn is 50 mm. This differential in sizes causes the filter to act like a traditional carb with the choke partially on. It lowers the "atmospheric" air horn pressure to much which allows the needle/main jet to draw away too much fuel.
The only advantage to the smaller air filters as far as I'm concerned is to make it easier to R&R the carbs. If the bike is running right there is no reason to be R&Ring the carbs.
Further, the rubber tube that connects the carb to the air box is actually a ram tube.(velocity stack) I'll bet that Yamaha spent more than a few development dollars on getting that tube just the right length and flare shaped to take advantage to increased HP & torque through mid RPM ranges.
If you go to allxs11's photo section look under Ken's Ratbyk and I have a picture of what I'm running at present. It is these ram tubes removed from the air box, mounted in the original position. I have covered the ends with a fine stainless steel mesh screen. These screens I picked up locally from K-Mart in the Martha Stewart section of housewares. They are small strainers for tea or whatever. They had a small wire handle on them that was spot welded onto the mainframe of the strainers. I simply snaped the handles off. The screen fits perfectly over the flare on the end of the velocity stack and it holds itself in place. Not to worried about dust up here in the N/W at present. Rains have already started. There is no dust. The screens keep out rocks, birds and small boys.
Sounds SUPER! There is a real throb from them under acceleration.
Ken/Sooke
78E Ratbyk

[xjguy]

You guys are really starting to talk me into staying stock-no problems so far other than have to hand throttle first ten seconds cold.

[kenkrieger]

My 81 is the same way ,10-20 seconds when cold and then hse's ready to drive. Although i9t is getting a bit sluggish between 1500-3500 rpms, might be time for a triple clean, or some techron first. I really did like the sound of those carbs pulling atmosphere with the airbox off though. My bud still has a set of those cones laying around, so I might be having to give it a try,,Just for tinkerins sake. All you folks have talked me into it. Thanks, appreciate it.

[Mike Hart]

Happiness is getting a phone call saying your bike parts have arrived My size 50 Mikuni pilots are here, I can get them at 10am tomorrow, I hope to have a report about it by tomorrow eve if non-bike life doesn't intervene....

[Wayne]

Well Ken I comfirmed that I was having the same probs you were. My cones did have the shoulder you spoke of, plugs were dark and the bike ran like crap.
I took the cones off and reinstalled the original air box with my K&N filter and, voila, all is as it was. She runs great again, cranks up the same.

So I guess I have a set of brand new cone filters for sale

Oh, and Mike...
I didnt know there was such a thing as a "non-bike" life.
Life without a motorcycle is no life at all!

[ratbyk]

Cones-thuuumpoos/with slober

Hi Wayne, just got back from a 2 day ride over in the coastal mountians. Feel great but a bit buzzed.
I was able to return my cones. Have not seen the credit yet/ the cones are likely still in the mail on their way back. I had purchased them from; mikesXS in Florida. When I had trouble with them I sent him an E-mail explaining my difficulties. He said to return them for cedit,"no problem!"
He also said that he has sold between 800/900 of them withoiut problems.(find that hard to believe, unless his supplier just changed over to these ones with a shoulder in them.)
Ken

[Mike Hart]

Got the 50 pilots in, and it started without the choke! It has never done that before! Feels strong. Will go for a ride later and check plug color.