Smoke on restart SXR

Manbearpig · 02-27-2010, 09:10 AM

Hey guys,
Was in the surf yesterday and my ski is starting to get hard to restart when its hot. I am having to feather the throttle a bit to get it to restart and when it does there is a plume of dark grey smoke (super rich) out the exhaust initially then it clears out. It is also starting to load up a lot at low speeds and requires a throttle burst to clear it out. It always clears out fine except when I need to restart it. I have messed around with the idle speed scew and low speed jet setting to no avail - even turned the low speed all the way in. I measured my popoff pressure and I am getting 27 PSI on both carbs. This is tested with a brand new mikuni guage - I am a bit worried as I have had this from new and have not changed the n/s or arm/springs. I know it should be around 38 psi. Is the above classic symptoms of leaking n/s?
MBP.

faster7581 · 02-27-2010, 09:21 AM

broken reeds? or hanging open maybe..

VEGAS 21 · 02-27-2010, 11:47 AM

Yep, check those reeds.

Manbearpig · 03-01-2010, 09:58 PM

Thanks,
I'll pull the reeds and report back.
MBP

Manbearpig · 03-29-2010, 01:07 AM

Guys,
I still have this problem. I pulled the reeds when I rebuilt my top end and they were perfect - no cracks and sealed correctly. I also inspected the carbs and noticed that the arms on both carbs were about 2mm too high. I reset the arms so they were flush with the body and changed my stock N/S to 2.0 as I wanted to eliminate them leaking. I just ran it on the hose to dial in the low speed.idle circuit and I can get the smoothest/highest idle with the lows at 1/4 turn out (80 pilots). Problem is once again if it idles for say more than a minute and I rev the throttle I still get some plumes of smoke then it clears. It is also fairly smokey at idle. Compression is at 185PSI on both - I have leaked checked the engine and no cracks in the hoses. Can someone also please confirm for me that on a hot day when you remove the fuel cap there will be some pressure release - ie same as a car. I know there is a pressure relief valve but have no idea on the setting. Any help at all appreciated. I will try and post up a you tube vid.
MBP.

RacerX2 · 03-29-2010, 01:46 AM

pressure in the tank is normal, I suppose it can get as high as the pop off setting in your carbs
some guys put restrictors in the carb return lines to get the system pressure up too so some pressure is good

mcn6 · 03-29-2010, 01:54 PM

Yup, supposed to have a little pressure in the tank, the check valve lets air in and not out... Sure sounds like leaking needle/seat or the pop off is too low??? Next time you come in, pull the flame arrestors and check to see if gas is dripping from the venturi, it doesn't take much to flood it. Might also relieve the tank pressure by venting it with the gas cap as soon as you come in, see if that helps.
1/4 turn out on the low needle... That being the case, the off idle rich condition is related to the above. Fix the first problem and you will probably be opening up the low needle to keep it from hesitating...

RD211 · 04-05-2010, 08:47 PM

what oil are you using?

Manbearpig · 04-06-2010, 12:26 PM

Quote:

what oil are you using?

http://www.penriteoil.com.au/product...two_stroke_oil

Penrite MARINE OUTBOARD
TWO STROKE OIL
Premium lower smoke two stroke oil manufactured
from selected base oils and an ashless additive system.
It is pre-diluted to facilitate easy mixing with fuel.
APPLICATION
All water cooled two stroke outboard engines
including oil injected and premix systems at ratios of
up to 100:1, depending on manufacturer requirements.
Marine Outboard Two Stroke Oil is NMMA Certified
for service NMMA TC-W3 at the engine
manufacturer’s recommended fuel/oil ratio.
May also be used in two stroke motorcycles and other
engines that require JASO FB two stroke oils.
CUSTOMER BENEFITS
• Minimises plug fouling, pre-ignition, ring
sticking and exhaust port blockage by
controlling deposit formation.
• Provides excellent anti-seize and anti-scuff
performance.
• Suitable for use with lead replacement and
unleaded petrol.
• Correct viscosity for consistent flow rates in
oil-injected engines.
• Improved smoke control with a very high
pass in the ISO EG-B requirements.
• Meets detergency, lubricity, torque and
varnish requirements of ISO EG-C and JASO
TC.
INDUSTRY SPECIFICATIONS
NMMA TC-W3 Certification Number RL-20076H (2006)
NMMA TC-WII JASO TB ISO EG-B
Density at 15oC, kg/L 0.873
Colour Dark Blue-green
Flash Point, oC 115
Viscosity, Kinematic, cSt
at 100oC 8.6
Sulphated Ash, mass % <0.01
Base Number 10.4

I'm running this at 40:1 . It is still playing up - nothing major though runs well but I could do without the smoke plumes after a long idle or hot start.

Quote:

Next time you come in, pull the flame arrestors and check to see if gas is dripping from the venturi, it doesn't take much to flood it.

Is the above check with or without motor running? I guess the next stage is to take the popoff back to the stock 38 PSI.

Cheers,
MBP.

mcn6 · 04-06-2010, 02:27 PM

This test is if it is still hard starting due to a leaking needle/seat. Test with the motor off.
If the 2.0 needle/seat cured the start problem and you are still rich on the idle circuit start turning the low speed needles in. Read the info below starting at pg.12 and especially pg. 22 and 23.
http://www.mikuni.com/pdf/sbn_manual.pdf