Get rid of Dynojet kit in my Big Twin?

[yankee dog]

This is a 94 fxdl, 27,000 miles, new to me. Has a K&N air cleaner and screamin eagle mufflers on stock pipes (with crossover). No other mods that I am aware of, still figuring out this bike.

Just dug into the carb because the bike acts lean at low speed (pops and coughs, burble on deceleration) but plugs and pipes look rich and strong exhaust smell.

Found what to me looks like a dyno-jet kit installed in carb. Looks like dynojet, not the thunderslide (based on google pics).

Main is 180, and slow is 42. I know I need to jump up to a 45 slow. Idle mix screw was at 3.5 turns. I also just cleaned the carb. Had some carbon build up on idle mix screw, mix screw packing O ring, washer, and spring still intact. Otherwise, carb a little dirty, but nothing obviously bad.

Diaphragm looks good with no holes, plastic near diaphragm has a little surface burn spot to it (what causes that plastic to burn?) but nothing I can feel and no distortion. The slide piston needed a little cleaning and polishing, hole in slide piston HAS been drilled to 1/8". Needle clip is on 3rd from top groove and it had 3 washers on top of the little needle clip. What is the purpose of the washers on top of the clip? I thought they were used as shims under the clip???

Anyways, should I try and plug the slide piston hole back up with JB weld and redrill? Should I just put in the 45 slow jet and then reinstall as is to see how it runs?

Was also thinking of returning to stock configuration which would mean new emulsion tube/main jet holder, needle, and diaphragm/slide piston (if I can't jb weld it). I was thinking of the older sportster needle, and of course the 45 slow jet, and keeping the 180 main.

Any suggestions? I have read pros and cons on the dynojet kit, so not sure which way to go and looking for any advice. If I can save myself from buying a new piston/diaphragm, then great. I also read something about a rivet for plugging the piston hole (reducing its size), but not sure on that fix? The other parts are do-able from a $$ standpoint.

Just want to get it tuned right, the plugs were so nasty one would not fire till I ran it through the plug blaster/cleaner. Thanks, YD

[yankee dog]

Correction, clip is in the 4th groove from the top on the needle. And the diaphragm/piston spring measures 5.25 inches fee length. I think the stock is 5.75 long? So will need one of those as well. Thanks, YD

[92Fatty]

I wouldn't bother with slide. 1/8 recommendation was on nightrider may years. I drilled my slide with a 7/64 bit and do not have any problems. I figure your your idle mixture is screwed out so much since you have a 42 slowjet.  I'd buy the parts to fix the bottom back and run it with the slide you have. I like the 88 sportster xl needle along with 45 and 180/185 combo.

[yankee dog]

Yes, thanks 92Fatty, I just ordered this kit:

http://www.harley-performance.com/stage-1-carb-kit.html

Looks like it has everything I need to bring it all back to "near normal". Gonna go with the 45 slow and keep the 180 main. The kit comes with 2 each of the slow and 2 each of the main, but it does not say what sizes they include. I guess they know what they are doing and will send me what I need.

I also ordered the ez just mixture screw and gonna go from there. Thanks for the info, new to the CV, my last bike had the keihin butterfly carb (1987) so charting in new waters...Thanks YD

[ViennaHog]

Over here the shop guys use the stock spring, the stock slide, the sporty needle xxxxx-88 shimmed with one or two 0.25mm washers, a 44 slow and a 175 main as a starting point. No fancy kits, just stock stuff in a matching configuration. Works in almost stage 1 mild cam applications.

[yankee dog]

ViennaHog, yes, thanks. That's what I am trying to get back to. Original configuration with just the few changes like you mentioned.

The kit in the link I provided is the sporty needle, and I guess the spring is similar to stock but "improved". Not sure what that means but will soon find out. The stock spring is 5.75 inches long. The spring I currently have is 5.25 inches long. If I need to, I will get the stock spring.

The slide piston has been drilled, and I will figure out a way to reduce it's size if I need to (jb weld?), and when the new carb parts show up, I will put those parts in, re-jet it, and give it a go from there.

Anyone know what or why the burn mark is from on the plastic near the diaphragm? Just curious. I think I figured out why the washers were on top of the e-clip (on the needle) but still curious about the burn mark. Thanks YD

[JBarrettB]

Those three washers are stacked on top of the clip so that the needle doesn't float up and down in the slide.

JB 

[ViennaHog]

Burn marks from backfiring through the carb would be my best guess. Plastic slides ...Wheeeew.

Saw a Vmax the other day that had been sitting for a few years. Plastic slides all stuck due to expansion...............there is a place for metal in my world

[martida01]

I pulled the DJ kit out of my bike.  Never could get it to run right.  It was a pig on fuel, and now pulls a lot harder with it back to 'stock'.

Go back to the stock emulsion tube.  I dropped in the N65 needle.  Also JB's my slide hole and redrilled.  Not sure if it was worth the effort.

This guy will have the parts for you:

http://www.cv-performance.com/carburetor-parts/

[yankee dog]

martida01, yep, that's the same info I found and was gonna post it, but you beat me to it!

I will post the info I found out over the past few days for others, but I went with the CVP kit which has a new emulsion tube, 180 main, 45 slow (may bump it up to 46 but need to do more checking/adjustments) and the n65 sportster needle.

While it has been a driving rain here in Michigan for the past few days (just put things back together last night), I can tell the bike starts easier, and exhaust does not flood the garage with that thick nasty burn your eyes exhaust like before the change out of carb parts. No cough, spit, or sputter either!

The other thing I noticed was the dyno-jet needle was extremely blunt profile on the tip, and the emulsion tube had like 2 holes in the side where the CVP emulsion tube has many, many emulsion holes, I think more than the oem tube. I used the CVP spring as well.

The info I found was stock cv slide vacuum port hole size is .097 in. and it is suggested to just clean up that hole with a 7/64 in drill bit (which is .105 in).

Direct quote from Ken Mendelson at CV Performance with regards to the "CV Slide Vacuum Port" (the official name for the CV carb diaphragm/piston slide off center vent hole). The only thing I would ad is, I don't like silicone sealer with fuel. It swells and breaks down with gas.

When filling the hole with jb weld, I would run a similar sized thread tap thru the hole your about to plug, clean with carb cleaner then fill with jb weld. The threads will provide a better bite or hold for the jb weld.

Ken Mendelson quote is in bold type :

"A 7/64 bit is about the closest you an get in a fractional drill bit, unless you have access to metric size bits. The actual hole size in the slide is approximately 2.6mm but the machining process generally leaves them smaller or partially blocked. A 7/64 bit is 2.78mm. As a reference a 1/8" bit is 3.18mm, but since most use a hand held drill the resulting hole can often end up in the 3.25mm range or larger.

A slide with too large of a hole can act like a shock that has lost it's dampening. The hole acts to regulate how fast the air above the slide can be displaced as the vacuum changes and draws the slide upward. The same applies as the slide attempts to return to a closed position, and just like a shock if it is allowed to move too quickly you end up with a slide that bounces and hunts for the proper position.

If the hole has been drilled larger than 1/8" I suggest either replacing the slide or modifying the slide by way of filling and re-drilling. Since I've always been sort of a cheap guy I can't see throwing away a slide and dropping $40-50 on a new one. I've had success repairing over-drilled slides by doing the following.
1) Fill the over drilled vacuum hole with JB Weld. Hi-temp silicone will also work.
2) Drill a new 7/64 hole adjacent to the old hole.
This method will salvage a perfectly good slide from the garbage and keep a few $$ in your pocket.

I should also mention that cutting the slide spring (another weak attempt at performance) is never recommended. Cutting the spring shortens it's travel but has an adverse effect on returning the slide to it's original position. If you want better throttle response use either a SE race spring from a 44mm carb or the CV Performance slide spring which has been designed with the correct length and tension. When used with the vacuum hole at stock or 7/64 you will have the correct balance of tension, travel, and slide response."

Hope this info helps others! YD

[martida01]

Be sure to let us know how it runs!  I know I struggled a bit (pulled my hair out) with mine until I removed that DJ kit. 

[CW#]

Over here the shop guys use the stock spring, the stock slide, the sporty needle xxxxx-88 shimmed with one or two 0.25mm washers, a 44 slow and a 175 main as a starting point. No fancy kits, just stock stuff in a matching configuration. Works in almost stage 1 mild cam applications.

I have heard drill the idle screw and add the sportster needle, adjust it first, then readjust for performance as needed (both the needle opening timing and the idle screw). Does this still mean, in your experience, that you would need to change the slow jet?

[yankee dog]

Here's my 2 cents: The slow jet is lean from the factory and that is what causes the coughs, spits and sputters (carb farts). Stock on my bike is 42 and that is way lean. Most reading I do says 45 is "bout right" and I have that in currently.

The idle mixture screw is the screw that is hidden or covered by the aluminum plug to make it tamper resistant. That aluminum plug is what needs to be drilled then pulled out by screwing a sheet metal screw in the hole you just drilled and pulling the plug out so you now have access to the idle mixture screw. There are specific instructions posted on the link I provided earlier about how to adjust that, but your basically adjusting it to achieve the smoothest and highest rpm when the bike is at a set or fixed engine speed (too lean makes the set rpm's drop and engine bog, too rich makes the set or fixed engine rpms drop and bog. Optimal setting should be around 2 1/2 turns out from the lightly seated point on idle mix screw (lightly seated would be 0 and then count the full turn out or loosening). Again read up on how to do this as I am just posting a summary.

If you need to adjust the screw more than 3 turns out to get smooth running and then no change, then you probably need to jump one more size higher on the slow jet (say a 46). Trying to get the max smoothness and rpms on the idle mix screw at about 2 1/2 turns out is where the sweet spot seems to be for the idle mix screw.

AS far as the needle and how it comes into play, I defer at this time as I am still doing my homework on that.  YD

[mkd]

joe minton's take on stock cv carb adjusting!          http://www.Americanrider.com/output.cfm?id=1815121                                                                                                 
 
First: The idle-air mixture screw

The factory's idle-air mixture screw setting is too lean for best performance and it should be adjusted. This is true for all stock as well as altered engines. Here's how to do it:

1. Remove the soft aluminum plug at the bottom of the carburetor that covers the air mixture screw. You will need to remove the carburetor to do this.

2. Turn the air screw all the way in until it lightly—and only lightly—bottoms. Turn the screw out one turn as a starting position.

3. After re-installing the carb, and with the engine warm and idling, use a small screwdriver to turn the screw slowly out until the engine begins to run unevenly.

4. Now turn the screw inward counting the turns, until the engine runs unevenly.

5. Finally, back the screw out halfway between these two "uneven" points. It's likely to end up between one and two turns out from the original stock position.

Second: The jet needle

The most important change, and the only item normally needing replacement, is the jet needle. Use one from an early Evo Sportster (H-D part no. 27094-88). It has a very slightly smaller diameter (0.0004") in the straight section above the beginning of the taper.

The new needle slightly richens the part-throttle mixture and is responsible for nearly all the improved running qualities this procedure provides. Mileage may lessen by one or two mpg in a stock engine. Modified engines often improve by a like amount.

Also, the stock slow-speed (idle) jet that is accessed from the float-bowl chamber should be correct and rarely needs replacing. Poor idling is almost always a consequence of the factory's lean mixture- screw adjustment. Do not consider replacing the jet until after you have re-adjusted the mixture screw, changed the jet needle, and thoroughly tested those alterations on the road.

If the engine continues to run lean at or just off idle (hesitates or "pops" into the air cleaner), you might need to replace the stock slow jet with the next larger one.

Street bikes seldom run on the main-jet circuit. The main jet has no function or effect below 3/4-throttle and then only in the upper half of the rpm range. Since the stock main jet is overly rich to begin with (by one or two sizes) it is seldom necessary to change it. Really—hardly ever.

Engine break-in: A proven technique

Another popular question is engine break-in. Your new Harley engine is pretty much ready to do business out the dealership's door. Most of its parts turn on roller or ball bearings. Engine break-in consists mostly of seating the piston rings. You can do this in about 15 minutes and a few miles down the road.

I, and very many other riders, mechanics and race tuners, use the method outlined below. It is proven and effective. I've been using it for more than 40 years and it does not reduce the life of an engine. You can do this even when using synthetic oils, which I recommend for more engine protection.

1. Upon assembly, only lightly oil the pistons, cylinders and rings.

2. Do not run the engine until you are ready to put a load on it. Make all tuning and safety-related adjustments before you start the motor.

3. Point the bike at the street.

4. Start it up and ride. Get into third gear with the engine near 2,000 rpm. Apply full throttle.

5. When the engine reaches 3,500 rpm, close the throttle and let the bike coast back to 2,000. Do it again 10 times.

6. You have just seated the rings. The idea is to place a load (pressure) on the top and second piston rings so they can "file" themselves into conformity with the still slightly new cylinder walls.

This method alternately loads then cools and lubricates the rings. Full throttle forces them into hard contact with the cylinder walls; however, the coasting phase cools and lubricates them. Simple, effective and proven.



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[yankee dog]

MKD, great info, am saving those for future reference...

Just took bike out for a ride. Ice pellets to the face was fun. Anyways, spit, sputter, and carb farts are gone. Acceleration is great, nice and smooth.  Never really got a chance to check out main jet fuel circuit (did not go fast enough-just stayed local) so I need to wait and see on that. Slight burble on decel. Not like before the carb tune up.

My initial thought would be to go to a 46 slow jet because of slight burble on decel and because of the following: When I adjust the idle mix screw (turning out from lightly seated), the engine rpms increase and continue to increase till I get to about 3 full turns out, then no further increase in rpms and NO DECREASE either. So that tells me I am still a little lean on the slow circuit, however:

I am now thinking I should pull carb off and intake manifold to replace intake O-ring seals. I am gonna go out and do the propane or carb spray test before I do that, but I really don't mind having to replace them anyways as I am sure they are original and it's probably overdue anyways.

The only other issue I have (and not sure if it is  an issue) is when the engine is at idle say 900 rpms, I can see fuel coming out of the orifice that the slide needle enters in the main throat of the carb at the bottom. I guess best way to describe it is, when looking into carb with air cleaner off, the needle splits down the center of the main throat. Where in enters the bottom of the main throat, while idling, I see fuel being sucked into the carb from this lower entry point. Not sure if that is normal or if the needle jet (link to pic below) is worn out from the old dynojet over sized (blunt) needle. Anybody have an opinion on that?

http://www.cv-performance.com/cvp-needle-jet/


Still need to check the plugs and will wait till the engine cools down a bit before I do that. Don't think I will get another test ride in today as it is starting to snow now and then rain on Monday! SUX! Thanks for all the info... YD

[yankee dog]

Well, as I suspected, front cylinder intake seal: When I hit it with carb spray at the cylinder to intake flange rpm drops and idle gets rougher...propane did nothing to change rpms. YD

[Hossamania]

If you haven't changed them before, they're pretty straight forward. But I had to cut down an allen wrench to fit in there.

[yankee dog]

I have changed out sporty's before. Looks pretty similar. I use grease when installing them and have not had any problems with leaking after replacement.

Yes, I have the cut down allen, the garbage disposal wrench tool thingy (trimmed down as well), and a custom made box end with a short piece of allen wrench welded to it. Using all three of those gets the job done. I should probably get some replacement 12 point bolts to make it easier for reassembly/future disassembly.

Sun came out and things dried up so I took the dyna out for another ride. Wow! Got her warmed up for a few miles and then jumped on it. Can't really complain on how it is running. Before I knew it I was doing 95 in 4th. Acceleration seemed clean and no lags. Just kept pulling nice and steady and smooth.

Letting her cool down to take another look at the plugs. Guess I should go get the bike registered this week. Thanks YD

[92Fatty]

Congrats on the fresh runner. It is always a good feeling when a plan comes together.