Dynojet Problems

[Anonymous]

Carburator needle height adjustment and assembly

My carburators had a "top hat" of sorts which was set in the needle slide and then secured with a circlip. I believe the spring was slipped on the needle, and then the needle inserted into the slide. The washer went on the TOP of the needle before inserting-the top of the circlip. Adding more washers would LOWER the needle, thereby making the mixture LEANER.

Also, the "tit" on the plastic "top hat" (a white plastic thingy) is supposed to TIP THE NEEDLE to one side. This makes the needle rest against one side of the needle hole in the carburator body. Why? So vibration does not destroy the needle.

The above was on a Suzuki 750EZ, 1982. I'n not sure if Mikuni or Keihin, however, they used the large diameter main jets. I believe they are like yours.

The plastic washer you talk of is about maybe 0.150 thick by memory and mind measurement. The manufacturers used this to set the needle height for stock and made it one piece so the needle height was fixed. You can buy washers off the shelf and some places that will work. Watch the diameter and make sure they are "burr free" and the same thickness as each other so the carbs remain balanced.

Comments? Happy motoring. Dieter

[Anonymous]

E-clip vs "tit".....

Mike J

The "tit" on the plastic top hat that is held in by the large circlip in the slide body is NOT meant to fit into the needle small circlip at all.

You must have at least one washer on top of the needles circlip in order to prevent the tit from going into the opening on the circlip. Yes, I see quite clearly you did not place washers on TOP of the needle, between the "top hat" and therefore you are running your needles quite high. ON the order of an 1/8 inch or so or 0.125. That's alot.

If you drilled out the hole on the bottom of your slides - which the dynojet kit recommends, this causes your slides to come up quicker, and to ride a little higher for a given vacuum (throttle opening) so you get better acceleration. I believe this IS your problem - having the needles too high.

The assembled order from top to bottom is......

Large circlip

Top hat

next on the needle.....which is "covered" by the top hat and inserted into the slide body, the order from needle top to bottom (bottom goes into the slide body) is:

Washer(s) (plastic OR metal is OK-use correct amount)

Needle circlip

spring

insert into slide needle hole

ON Hondas, the arrangement was a top hat but the spring was inserted in the top hat first. Adjustment was made by changing the washer thicknesses UNDER the needle circlip. From what you describe, you do NOT have this arrangement.

- Dieter

[mike J]

Also, the "tit" on the plastic "top hat" (a white plastic thingy) is supposed to TIP THE NEEDLE to one side. This makes the needle rest against one side of the needle hole in the carburator body. Why? So vibration does not destroy the needle.


Well if that's the case I just ruined my 4 "top hats" as you call them. That's what was so crazy about the whole matter, it would make the needle tip to one side and that's why I kept saying that had to be wrong. Damn it to hell, for the life of me I've never seen anything designed like this!!!! Well I guess I'm screwed now, I just refused to believe that was correct because of the way it fit. I hope to go run the bike tomorrow and see what it runs like but looks like it back to the suzuki shop for parts again. Anybody got a match and some gasoline? Mike

[mike J]

Tony, where were you two weeks ago?


But seriously, thanks for helping clear this up

[KEITH KRAUSE]

mike j, if the "tilted' needle was what was bothering you, you should have said so earlier. That's normal. The needles are always a little "springy" and go to one side. When lowering the slides/pistons into the carbs, you always have to straighten/guide the needle into the needle jet because of this.
Water under the bridge now. :roll: Hope the bike runs good when you get it together. Let us know.

[mike J]

Keith, yea the tilted needles had me all out of wack. I guess I should have made myself clear. Well anyway rode it down the road today and it still runs like *@%^$*@%^$*@%^$*@%^$. I'm beginning to think that this bike just doesn't want to run right. I put in 160 air jets from Dynojet because the bike would crank virtually w/o the choke. Now the bike seems like it's running out of fuel. There's an in line fuel filter on the bike and it's got me wondering. Has anyone had any experience(bad) with one of these? Mike

[katman]

There's an in line fuel filter on the bike and it's got me wondering. Has anyone had any experience(bad) with one of these? Mike

Throw it out..

run a strait line. the petcock has a filter on it. Unless you make your own gas? or your tank is all rusted out.

[KEITH KRAUSE]

There's an in line fuel filter on the bike and it's got me wondering. Has anyone had any experience(bad) with one of these? Mike

Throw it out..

run a strait line. the petcock has a filter on it. Unless you make your own gas? or your tank is all rusted out.

EXACTLY what I say. Those things cause more trouble than they stop.

[KEITH KRAUSE]

mike j, whattaya say we start over with what's wrong with the bike?
It's a little easier than going back and searching what's happened so far. It might get more people involved too. Before we can help with the re-jet, you have to be certain the needles are assembed correctly. Are you going to have to re-order parts to get them right?
Once you run the bike with a correctly assembled needle and get some reads, we can start over with performance problems and what mod's you have, etc.

[katman]

Mike,

that is good advise from keith. sort out one prob at a time from the beginning and move on from there. starting with the carbs.

Maybe you can get a hold of some doner carbs to try. if they don't work either the problem is elswere.

I have known situations where guys (including me) have spent loads of time on the compicated stuff and all that was needed was to "plug it in"

it may save some time an agri....

A buddy of mine spent weeks sourcing an idling probem he thought was a carb prob. and it turned out to be a spark plug wire.

[mike J]

OK guys heres the latest and greatest. I went out today and ran about 1-1/4 tanks of fuel through it. As for carb seeting here's what they now are. Air Jets are the DynoJet 160 option. The needles are using my machined delrin spacers but they are the same length as the stock ones, The needle is in the second from the top position. The Mains are Dynojet 138's. The mixture screws are set at 3 turns outs. Seveal things I noticed different today. The bike is much more responsive in the 3- 4K range than before. I think the new air jets helped here as the bike now needs morechoke to crank(cold)as it almost needed none before. The bike is now missing (sounds and feels like a lean condition) when you roll on and get on the throttle. Now take into consideration the the plastic *@%^$*@%^$*@%^$*@%^$ are now gone from my "hats" . I'm not using the Dynojet metal washers on top of the needle as I could see no good use for . The bike runs really good at crusing (5k and below). Also oneother thing I noticed was the buzzing right handle bar that I spoke about before is now gone.
I have a new Morgan sync gauge but I haven't used it yet because the bike is still too far out ( missing in the mid range) So when I came in tonight I pulled the plugs and the outside (rim) of the plug is very black but the center and the tip are white so I'm guessing that's it's lean in the middle. I get a small amount of popping when I roll off the throttle but my thoughts are to richen the needle and leave the mixture screw as is. Anyone got any suggestions? I'm probably goingto order new "hats" for the needles Monday as well. Mike J

[RacingJake]

I'm not a fan of K&N Dyno jets due to the fact they are smaller in size when compared to standard oem jets. Some where there is a chart showing what the real sizes are. 138 = 133 I think. Go ahead and install some real jets like 150's and your problem will be gone.

I did the same thing last year with a Dynojet kit put all that stuff in and the bike ran like crap, put the oem needles in with 150's and the bike ran great again. Thats was 34mm cv carbs on a 1075 motor. Dyno jets are not apples to apples it's more like apples to pineapples. As for the jet kit it's at the bottom of my tool box.

[KEITH KRAUSE]

The jet kit needles are meant to be used with all of the stock washers/spacers, unless the instructions say otherwise. If you leave something out, it will change the conditions the new needles were machined for. Also, will the new "hats" change the needle height compared to the old ones you modified?
You're obviously running lean. I'm not sure what to suggest yet because of the needle situation.
If you have a safe place to do higher speed tests, I suggest marking the throttle and doing some chop tests for the main and needle circuits. A mile or two at 1/3 throttle and the same distance at fully open.
Just to re-cap, I assume the carbs are clean, the floats are adjusted within their range, no possible manifold/o-ring intake leaks, the carbs are at least mechanically synched, the floatbowl vent lines are removed, the vacuum orifices to the diaphragm chambers were enlarged, the filters are oiled, the ignition is timed and advancing correctly, the valve clearances are OK, the gas cap vent is clear, the entire petcock is clean, the vacuum line is good, the fuel line is 5/16" and there's no fuel filter.
All this stuff is basic before re-jetting. If you know it's all good, jetting is easier. The carbs have to be vacuum synched to get uniform/accurate reads. I know you said the jetting is too far off to synch yet.

[mike J]

the floatbowl vent lines are removed

Keith, yea they are gone, what's the reason behind this? I know on the old KZ's they require a certain dia tube and a certain length to make the carbs work correctly. Mike

[KEITH KRAUSE]

the floatbowl vent lines are removed

Keith, yea they are gone, what's the reason behind this? I know on the old KZ's they require a certain dia tube and a certain length to make the carbs work correctly. Mike

I called Dynojet years ago about this requirement in their instructions. This is their reason: With the increased intake with pod filters, a vortex effect is created in the floatbowl vent lines. This interferes with good venting. The venting can be even worse in crosswinds. This causes fuel starvation.
My added opinion/reason: Besides the vortex effect creating added resistance, the lines themselves create resistance. Since the intake has increased, you have to do something to help the venting "keep up" with the increase. Since we can't increase the size of the venting passages, the best we can do is minimize the resistance by removing the lines.
If you don't remove the lines, the compromised venting will not allow the jets to draw fuel as easily, causing fuel starvation. This is constant but most noticable at steady speeds.
The level of fuel starvation is not like actually running out of gas, but more like the hesitation you feel at the first sign of running out. I did a test with my 1000 and it ran terrible with the lines on. The second I removed them, it cleared up. Some carbs/bikes are more effected than others, but all are effected to some amount, except the newer bikes with pressurized airbox's.