Help me read my piston wash

[ou812]

97 SJ, B pipe mod, 185 PSI with ADA head, 135 mains and stock 70 pilots in stock 38's carbs.

Let me know what you think. I think it looks lean, though when I do plug chops at WOT the plugs have a good color to them. Would just going up to 72.5 pilots make enough of a difference in piston wash, or should I go up to 140 mains also? I think I'm between 1 1/2 to 2 turns out on the high and low mixture screws.

Thanks!

 

[Sospikey]

Looks leanish. Both low and high speed jets are available in 2.5 increments. What popoff are you running?
I'd get 72.5s and 137.5 and try swapping the 135 first. Try and see. If not differerent; remove and use 72.5. Try and see. Maybe someone who is better at carbs can comment?

 

[tor*p*do]

looks WAY to lean for me
I like nice semicircles of piston wash
read the cylinder head not the plugs
richen that beats up!!!!

 

[Waternut]

It does look lean but FP recommends the following:

Main Jet: 135 (130 stock)
Pilot Jet: 70 (stock)
High speed screw: 1 2 turns out from closed
Low speed screw: 1 1/4 turns out form closed
Needle & Seat: stock (55 psi)
Spring: Stock (95 gram)

If the ski runs like it's supposed to, I don't know if I'd change the jets though. Maybe just give the screws a 1/4 turn out and see how it does. If the ski has some dead spots then you should really look into fixing the problem ASAP.

 

[ou812]

Ski runs good, I just don't want to seize it up. I've probably ran 5-6 tanks through it and have had no problems. I went off what FPP recommended, but then again each engine is different.

I had some 72.5 pilot jets around so I put them in to try. I also opened the High screws a 1/4 turn and ill see how that goes once I can make it to the lake. I might get some 140 or 137.5 mains to try out since I am worried that I am to lean.

 

[ou812]

Going to get some main jets today. From the looks of my piston wash, should I get 137.5 or 140 mains??

Thanks!

 

[tor*p*do]

get both, start with the 140 and see how rich it blubbers
or not . . . .

 

[ou812]

Well they only had 142.5 in stock. I'll give it a shot but I Think that will be too much. I'll tune from there and see how it goes.

 

[kevbo]

Why are you changing the main jets? Are your top screws more than 2 turns out?

 

[ou812]

Why are you changing the main jets? Are your top screws more than 2 turns out?

I'm at 2 turns out on the high screws and from what it looks like, I'm to lean and would rather be safe. Though I really think the 142.5 are going to be way to big.

 

[kevbo]

I think the top screws at 2 turns out are flowing more than the jet size difference but they may be getting close. The worst thing that can happen is that you will be too rich with the screws closed.

 

[Blue]

Wash

I have almost the same set up Im running 75 pilots, 80 gram springs and 140 mains at 1 turn on low and 1-1/2 on high and my pistons look like yours. I also cannot get the out ring of the plug to carbon up which Ive heard is a sign of being lean. Im think of going to 145 mains just to get a better wash pattern. My ski rips but maybe it will be better with the 145 jets.

 

[Waternut]

Well I don't mean to thread jack but I think this is kind of related. If your piston wash is either super clean or super black but the engine runs amazing and small carb adjustments make it run worse... How is that possible?

For instance, my wiseco pistons have been in my SJ for 5 months now and look almost as clean as the day I put them in. Knowing that the piston wash shows that my mixture is super rich, I leaned the carb a 1/4 turn on the high and low and the throttle response was no where near as clean. I don't get it...

 

[tor*p*do]

Well I don't mean to thread jack but I think this is kind of related. If your piston wash is either super clean or super black but the engine runs amazing and small carb adjustments make it run worse... How is that possible?

For instance, my wiseco pistons have been in my SJ for 5 months now and look almost as clean as the day I put them in. Knowing that the piston wash shows that my mixture is super rich, I leaned the carb a 1/4 turn on the high and low and the throttle response was no where near as clean. I don't get it...

what oil you using? some burn really clean

 

[ou812]

I ran the 142 and 72.5 jets this weekend and it seemed to run just as well as before. When I put in the bigger jets I put the screws at 1 turn out each. After riding I turned the highs in 1/8 to a 1/4 turn and all was good.

I'm still playing around with screw settings on the b pipe and cant seem to get that prefect yet. It seems every lake I go to I need to adjust the screws. Does lake water temp play a big role in pipe tuning?

 

[Waternut]

what oil you using? some burn really clean

I'm running Pennzoil Marine full synthetic. My kawi pistons are typically clean as well but not quite as much. Maybe it is just the oil but I'm hesitant to call that the final verdict.

I'm still playing around with screw settings on the b pipe and cant seem to get that prefect yet. It seems every lake I go to I need to adjust the screws. Does lake water temp play a big role in pipe tuning?

If the lake water is a noticeably different temperature than whatever body of water you ride in otherwise, it could certainly make a difference. Could be riding styles on different bodies of water or it could be something as simple as one body of water has a lot more white wash and you cavitate more because of it causing the pipe to run hotter more often.