I am getting my parts back soon from HPD and am planning to put my quad back together. I had it ported and added all the other speed mods available. I noticed that my Weisco has a blackish deposit/color on top. Is this normal? Has about 800 miles on it. Should I clean it off before reinstallation?

Maybe it's normal...but just want to be sure.

 

It is normal to have a black carbon 'film' on the piston. If it is very thick or flaky, I would clean it off with a little solvent and a SOFT brush, like maybe an old toothbrush.

 

Have you ever noticed that you usually don't see a lot of carbon on a seized piston? The combustion chamber temperatures must burn it off before the engine seizes.

 

Yes, it's normal. You can clean the carbon off the dome by removing the piston from the rod and soaking it in carb cleaner or parts dip and brushing with a soft wire brush, or glass bead blasting.
Now it's time to start adding some oil to the fuel( If you're not pre-mixing already ) to keep all of those parts lubed.

 

CaptNemo,

I am getting my cylinder back and a 39mm carb from HPD soon and was wondering if I should adjust the oil injection any? Does it adjust itself automatically in proportion to the amount of fuel used by the engine? I am keeping the injection system for now. Should I add a bit of oil to the gas anyway? Will this affect performance??

Brian

 

When you install the carb and adjust the throttle, you'll find that you don't quite have enough cable travel to open the slide all the way. All of the throttle adjusting will throw the oil injection adjustment way off. You'll have to adjust it as well. The cable splitter is what limits the travel.
I ended up removing the oil pump and put a single throttle cable on it to get all of the travel that I could, and started pre-mixing 32:1 with Polaris Gold oil. I'm still playing with the throttle adjustments to get it perfect.
I would say that Polaris' break in lube ratio ( I don't have it here in front of me right now ) would be the minimum that I would use in a heavily modded 400 in addition to the oil injection.

 

Nemo, How did you come up with the ratio that you run?? I have the block off plate, and run Castor 927 and 100 octane at approx. 48:1. It still smokes a fair amount, especially at startup, and plug checks all indicate enough oil. I was just wondering if the 32:1 was a recommended ratio for running a pre-mix setup...

 

In a discussion with Rick Ritter, he recomended 32:1 over the 40:1 ratio that I was using at the time. In one of the technical papers on www.macdizzy.com, they tested a two - stroke engine with various fuel / oil ratios. They were increasing horsepower up to a 20:1 ratio, it was theorized that increased lubrication of moving parts and better piston ring seal was the cause of the HP increase.

 

A high proformance 2 stroke racer said to me 12oz golden specto to 5gal. of prem gas(be that 91, turbo blue or mix) you'll never blow another engine or fowl a plug due to ratio. Been true for him for 12 years. He races a 88 LT250R.