Super Jet TUNING HELP! PLEASE!! a point in the right direction or some advise

[BIGRED Z]

OK. I'm frustrated and in need of help. I feel I may have more on my hands than capable of but will try anyway. Last year I bought a motor that was built by #Zero. Great looking motor. It was built with NW sleeve and the specs are as follow the way I am running it now.

Here is where I am at now.

771 bb ported nicely and built by #zero

ada head with 35cc domes. Compression last year when I bought the motor 185-190 psi. Compression after rebuilt and base gasket was 205-210psi. (just checked squish @ .035?)

Just replaced the crank and replaced the cylinder base gasket with an aluminum base gasket.

I rebuilt a set of sbn 44's with an original mikuni rebuilt kits and set the carb up to
120p/125m 2.0 n/s 95g spring(Low 3/4 turn out-high 1-1/8 out)

aftermarket flame arrestors

running a factory b pipe (ported and cleaned) with a blaster mod chamber to an atp waterbox

skat setback mag with a 13/18 cutback impeller from Maniac with a medium cone

I went to water test the ski this past weekend (it was 38 degree w/t) and coasted around a bit to let the ski warm up properly. After about 5-10 minutes of low rpm coasting at about 1/4 throttle I started to play 1/8 throttle - 3/8 throttle making sure to stay under a half throttle pull. The ski brapped pretty nicely but every 3rd or fourth time of pulling the throttle she felt like she would fuel load and gargle pretty bad falling to almost a stall and then take off again. This seem to be a rich condition so we turned to low adjusters into 3/4 and test ran again. Same condition same throttle response. After reading the Mikuni Manuel for the um-teenth time we determined I was looking at possible to low on the pop off pressure and possible to large of a low speed jet. I changed the low speed jet to a 115 in both carbs and changed the pop off pressure to 28 psi with a spring change to 115g.

After putting everything back together and trying to start on the stand my ski wouldn't start and stay running without the primer being used. I pulled the carbs again and reinspected everything, sprayed my filters out and reassembled again. No she is starting but has an unmaintainable idle. Seems very high on one start and low on another start. (throttle cable is not pinched or pulling)

I was advised to check my squish just to know as much about my setup as possible and after checking that tonight it's at .035 which I know is not the ideal spot to be?!

It seems to me I have a bunch of spot that I need to address but could really use some help getting in the right direction so i'm not wasting my time as I'm trying to take this ski to wave daze and time is ticking!!!!

thanks for the HELP to anyone that can and if I missed some detail that needs to be address let me know!

Currently the cylinder head is pulled and the domes are out as I need direction on fixing the squish issue?

 

[Crab]

PM wax, Im betting something closer to this might work....
125 lows
110 highs
2.3 ns. 95 gram spring.

1.5 turns on low
1 turn on high t

 

[JetManiac]

Are you sure it wasnt too lean? Did you try richening?

Many will say .035 is too tight and to increase to .045". We have custom thicknesses of base gaskets to increase your squish.

 

[BIGRED Z]

Are you sure it wasnt too lean? Did you try richening?

Many will say .035 is too tight and to increase to .045". We have custom thicknesses of base gaskets to increase your squish.

The way it felt seemed to be rich. After a 5 minute ride the plugs were pretty dark and seemed to support that. After turning them into 3/4 I did turn them back out to 1 turn with no change in the bog down.

As far as the .035 I've been advise by a few people that it need to be increased and it is likely that the aluminum base gasket is to thin. I never did a squish test last year so I have nothing to reference it too. I really would like to avoid pulling the motor down again so I was hoping to have the dome cut if that is possible?

 

[KTM434]

Sounded like a lean idle and a lean bog off idle to me when I was reading your description also. Turn out the low and listen to idle change. Then re-jet more rich if needed (pilot). Crabs suggestion may work better for jetting

 

[BIGRED Z]

Can the plugs be dark and still have a lean condition? and if that is the case would that be why I have a poor idle on the stand seeing how I just leaned it out even more?

 

[Pro-pulsion]

When you tuned your carbs, did you sync them with a vacuum gauge to make sure both carbs are drawing the same volume of air? Some manufacturers only suggest using something like a 0.060" drill bit and seating the throttle butterfly lightly onto the bit to achieve synchronization but that is far from the truth. No carb parts will perform identically and so special vacuum synchronizing meters are needed to dial in each carb to perform virtually identical. Here is one that I was going to buy before I decided to get away from dual carbs.

http://vwparts.aircooled.net/Snail-Type-Syncrometer-Carb-Sync-Tool-GERMAN-SK-p/ste-sk.htm

 

[BIGRED Z]

When you tuned your carbs, did you sync them with a vacuum gauge to make sure both carbs are drawing the same volume of air? Some manufacturers only suggest using something like a 0.060" drill bit and seating the throttle butterfly lightly onto the bit to achieve synchronization but that is far from the truth. No carb parts will perform identically and so special vacuum synchronizing meters are needed to dial in each carb to perform virtually identical. Here is one that I was going to buy before I decided to get away from dual carbs.

http://vwparts.aircooled.net/Snail-Type-Syncrometer-Carb-Sync-Tool-GERMAN-SK-p/ste-sk.htm

no I havn't synced the carbs. I assumed that if both butteryflies opened at the same time all is well. What does this do to my current situation?

 

[waxhead]

Ok well got your pm so here we go.
As some one posted the specs above would be a good place to start.
Your main is way to big for your bottom. thats whats causing your gurgling issue. The low speed jet should really be called the every where jet the main is more of a trim to the major fuel flow.
Open the bottom end up to about 1.5 turns this will help your idle and starting alot
Go with about 20-24 psi pop off.
Zero does great work and the ski will haul when set up right.

This information is based on the assumption that your engine is all airtight and no other issues

 

[BIGRED Z]

Ok well got your pm so here we go.
As some one posted the specs above would be a good place to start.
Your main is way to big for your bottom. thats whats causing your gurgling issue. The low speed jet should really be called the every where jet the main is more of a trim to the major fuel flow.
Open the bottom end up to about 1.5 turns this will help your idle and starting alot
Go with about 20-24 psi pop off.
Zero does great work and the ski will haul when set up right.

This information is based on the assumption that your engine is all airtight and no other issues

the only other issue that I need to address is the squish which is currently at .035

is recutting the domes and antiquate solution to that? Or do I pull the motor again and swap out base gaskets? LMK

 

[waxhead]

No the squish will not be causing the issue. As long as the crank is in good condition you will have no issue with squish that tight

 

[socal750]

I was having a similar problem ended up being needles had gotten swollen from good ole ethanol I'm guessing,it would dribble on idle cause of low pop off but if I raised it the needles would stick causing all kinds of drama

 

[BIGRED Z]

Ok. I will re-jet the carbs as follow and just to make sure I understand ....... these will be reverse jetted in this set up right?

low speed jets(pilots) - 125
high speed jets (mains)- 105
low speed adjuster screw - 1 1/2 turns out
high speed adjuster screw - 1 turn out
n/s (new mikuni) 2.3 paired with a 115 spring should put me in the 22-23 psi range according to the book but will have to actually do the pop off test to verify.

I have already done a leak down test on the motor and it held 7psi for 3 1/2 hours so I'm pretty sure I am ok there

and just to verify again I am ok to run .035 squish as long as I feel comfortable with the crank I put it so I don't have to recut the domes or replace my base gasket?

thanks again

 

[speedysprocket]

My suggestion would be only one change at a time. Don't make a major pilot jet and major pop-off change all at once.
As for carbs dribbling at idle, you can run two or even three check valves on the block inside the carbs to help that issue. If it was me, I'd go back to your original set up and just lean the pilot jet. See how that performs. Then go up or down from there depending on how it worked.
Also, check your reeds! I've had bad reeds give me similar issues.

 

[BIGRED Z]

My suggestion would be only one change at a time. Don't make a major pilot jet and major pop-off change all at once.
As for carbs dribbling at idle, you can run two or even three check valves on the block inside the carbs to help that issue. If it was me, I'd go back to your original set up and just lean the pilot jet. See how that performs. Then go up or down from there depending on how it worked.
Also, check your reeds! I've had bad reeds give me similar issues.

reeds are brand new carbon tech and I did double check the reeds where still intact the last time I pulled the carbs off. I just checked the 2.0 n/s that I bought and they are not original mikuni part (don't know if it matters or not).

according to wax's, maniacs, KTM and crabs post it would seem I am dealing with a lean condition on my lows with a possible leaking n/s and a main that is way to big. I'm ordering all new n/s and jets and will use the above a my base and tune from there which seems like my best option at this point

 

[Pro-pulsion]

no I havn't synced the carbs. I assumed that if both butteryflies opened at the same time all is well. What does this do to my current situation?

All this will do is insure that both carbs are drawing virtually identical amounts of air per cfm as a matched set. It really only takes very small changes such as gasket overhang impedance, weaker or stronger carb rebuild kit materials, anything of that sort and you could have an imbalanced airflow. So if one carb is drawing a little less air, you will either run into too much fuel to air ratio going in one cylinder or not enough fuel charge entirely going in and causing lean or rich running conditions.

Info update: One thing I forgot to mention because I was at work and on the end of my break, but just to keep the clarity here you do still have to set your butterflies identically to each other such as using the 0.060" drill bit to set the air gaps on them. But once you have them set you will only be synching the carbs by use of the mixture adjusting screws (obviously the throttle linkage too but this is regarding fuel/air mix and proper cfms). That is how true synchronizing gauges work. Each cylinder will respond differently to the various mixture settings, but gauges like the one I was going to buy will tell you where the sweet spot is so you can tune both carbs to have a much more precise fuel charge mixture according to the cylinder's requirement. If you have had a chance to research carb tuning on twin cylinder 2-stroke engines you may have noticed that there is always a recommendation to have either the PTO carb or mag side carb a little more on the rich side. That is the reason for it, to sync the carbs according to fuel/air flow and ratio. It is not uncommon to find one carb in the area of 1/8th of a turn either way different on either the high or low screw setting, or both in some instances.

 

[waxhead]

You have to change all at the same time. other wise it just going to screw up the rest of the setup. Yes at 35 thou you will be fine with your squish as long as your crank , bearings are all ok

 

[BIGRED Z]

Ok. got her pretty close this weekend. Ended up with 115p/115 m, 1-1/8 turn low speed,7/8 turn high speed, 2.0 n/s with 115 springs. Spring arm slightly bent to achieve 28 psi pop.

A fresh set of plugs were turning a nice golden brown after a little ridding time. Unfortunately we were not able to check the plugs after a high speed run because of the water conditions so that will have to wait till a flat water day but she should be good for wave daze at least.


not that its a huge deal but with the compression on this ski being 210psi in each hole I am running 50% (110 octane turbo blue) and 50% ( 93 octane premium pump gas) along with the above adjustments that were made. The ski is set up on dual cooling but after riding for about 1/2 hour riding the cylinder and head were much hotter than my past setups. I know that compression creates heat and that the 100+ octane has a slower hotter burn than standard fuel which will add to that. But how hot is to hot? The dual cooling is routed to both inlets on the bottom of the manifold and then from the head to the fp head pipe and the other overboard. The reason that I am asking is we were riding in 40 degree water and all my pissers had good flow and the motor was still that warm. Any thoughts would be welcomed or if there is nothing to worry about even better. thanks

 

[speedysprocket]

When I went to a big motor, it was a lot hotter. I drilled out all my fittings (brass elbows) as big as they'd go to allow them to flow more water and it made a substantial difference in engine temperature.

 

[Haof]

Just read the original post, so kind of irrelevant now but... If any one else read this thread and is having the same issue.
I had an issue where my ski would run fine at low speed and fall on its face when I would get on on it. Or would run fine if I got right on it but would die off after a min or tow of hard riding. I adjusted carbs over and over, it seemed like any adjustment would only make a change for the first min or two still. Cut to the end of the story I finally pulled my hood off right after it started having issues and found out that my engine compartment was full of exhaust; one of the clamps had come off and I was leaking exhaust. I guess it was all clearing up before I got the hood open before that. Easy fix but drove me nut for half a day.

Wax also mentioned something to the same affect about being air tight.