any one know about reeding pistons

[jw.]

Originally posted by Matt
JW, what impact does the oil in a 2 stroke have? Does it change the colour to make it unreadable?

I didn't find it made a noticeable difference. However, it is giving an indication of plug temperature so it relies on the plugs being the correct heat rating.

On my merc, I never got all cylinders to read exacly the same. I reckon there is unequal fueling across the cylinders. Sometimes, there was a difference in colour side to side of the porcelain which indicated a big temperature difference at one side of the plug compared to the other. To be fair, I found it difficult to read the surface gap plugs because it's only possible to see the circular tip of the porcelain around the metal electrode. I did experiment with normal plugs and I couldn't discern a difference in performance and the plugs could be read.

My Suzi was different, it always read evenly across the cylinders and after extended cruising the plugs would be a light tan colour which is spot on.

Interestingly, the Suzi used normal plugs as standard and it wasn't able to fire the surface gap ones reliably at low revs. Once it got up onto the highspeed charge coils, it was fine. But in normal use it was hopeless with these plugs. I think this indicates a higher voltage is necessary to fire the surface plugs.

It is always a good idea to err on the rich side with a 2 stroke because a rich mixture gives a certain amount of charge cooling which gets more fuel/air into the crankcase. This tends to flatten the power/mixture curve and negates, to a certain extent, the fall in power due to an over rich mixture. Of course, it also tends to keep the engine running cooler too.

2 strokes will 4 stroke when the mixture is excessively rich.

In fact, a normal charateristic of 2 strokes, when the mixture is correct, is to 4 stroke until they are loaded and then they break into 2 stroke. Outboard motors don't seem to do this readily. I don't know why. But the higher the tuning, the less tendency they have to display this charateristic.

Listen to a chainsaw or a strimmer, they have a broken sound until they start to cut. If the mixture is slightly weakened they can be made to 2 stroke all the time but the max power drops off significantly.

If you have been into model engines, you'll be familiar with the same characteristic. In some model aeroplanes, where there is no throttle control, this is the method used to control the motor speed. When the plane dives, the load comes off the motor and it 4 strokes to prevent it screaming towards the ground. When it climbs it loads up and breaks into 2 stroke to give a good pulling power.

Anyway, I've started blethering, so I'll stop.

[Burty]

Originally posted by roofer
There's your answer, its running rich so you dont blow it up again.

Yeah but they should all be rich not just one side

[roofer]

Originally posted by Burty
Yeah but they should all be rich not just one side

Maybe he's only rejetted one side, the side with new pistons in.

[scottyboy]

What about the trigger boxes on the side of the engine? Each box triggers one bank of cylinders dont it? Maybe its intermitantly breaking down at high speed? But like cookee said if it was on three it would have no power in gear! If it was out of gear it would still sound like it was on six but as soon as you put it in gear it would "bog" out!

[scottyboy]

Originally posted by roofer
Maybe he's only rejetted one side, the side with new pistons in.

Would have thought was bad practice to jet one side of the carb?

[karl]

Originally posted by scottyboy
Would have thought was bad practice to jet one side of the carb?

all the jet are the same. 076

[JamesM]

Have a good look at em cus sometimes people drill em out bigger and you can sometimes see this visually if they've gone up a few sizes. Maybe matey put what he thought were all 76's in there but in fact where not.

[scottyboy]

.076 are big i think?And of course you have to take into account the facy that the engine maybe "worked" and ya dont know about it! Not really wanting to go into this because of the different types of carbs used and it makes alot of difference on the year of the engine aswell i think as to what jet's you should run!

[Jay Smith]

This is the way I check the richness and leaness of a motor that I am in doughts about and ALWAYS start out rich from where you even THINK you will need to be..

Run the motor to top speed and hold it for at least 15 to 30 seconds kill it clean if you can do it without backwashing over the splashwell and swamping the boat. Have someone let you stand on thier boat front or pull to the bank. Take off cowling and remove # 5 plug. Roll # 5 to BOTTOM dead center. With a "bend-o-lite" look at the intake side of the piston ( outside of the block toward the intake tracks ) if the piston is wet where the fuel vapor is crossing the crown about the size of a nickle ( us coin ) its pretty well jetted right. If the piston is wet across half the crown its too rich lean it down. If the piston is dry or ashy color richen up and quick. If you are having a motor on the top end laying down to determine wheather its lean or rich hit the key switch enrichener if the motor 4 strokes and falls on its ass it too rich if the motor picks up in RPM and power it was too lean !

Another thing to consider if you breaking in a motor and somebody has suggested to double oil it DON'T LISTEN the richer a fuel mixture is mixed with oil the heavier the specific gravity and the thicker the viscosity becomes it then will pass through the particular metering system ( jet or injector ) slower with the same amount of fuel pressure and the motor will be LEAN. Also oil holds, maintains and creates HEAT over and above what is the nessary amount for shear lubrication ... MORE IS NOT BETTER. Steel bored motors DO NOT LIKE syn. oils most syn oils do not have the load bearing propertys to prevent scuffing during breakin and as many as 50 hrs after breakin ( On steel bores ) Coated motors I suggest to customers to run 100 gals of pertrolium oil at 32:1 before going to 100 % syn. With the coated sleeved motors the bores and pistons are like materials and expantion rates between the two like material make ups are not as apparent as cast iron bores and alum pistons the coated bored aluminum sleeved motors retrofitted with aluminum forged pistons are less of an issue, thats the reason for the thicker sticker petrolium oils on unlike bores and piston materials ( cast ioron mated with aluminum pistons ) because they need the strong and thicker film between the two to prevent gaulding ! Also on steel sleeve motors retrofited with FORGED racing pistons the forged piston will expand more than a cast piston so one must allow more clearance ( .008" ) also leave the thermostats and poppet in the block the water must be stopped cycling through the block to allow the block to quickly build heat so that the sleeve can expand and try to "catch" the quickly expanding aluminum piston.........I fyou try to create a coated sleeve cooling system with steel bores the water quickly passing through the block and not being stopped by the thermoststs will never reach a safe heat and gaulding will occur. You can reduce gaulding by giving the piston to cylinder wall clearance but the motor will have a premature bad leakdown due to rocking of the clearanced piston...

Cheers !

Jay @ JSRE

[MARINER RACING]

JAY SMITH knows his stuff
whenever i have a question i call him
He is what we southerners call a YANKEE