should I go 50cc or 70cc two stroke cylinder kit? By nobodyspecial (Read 4,619 times)

[nobodyspecial]

Apr 9, 2016 20:11:38 GMT -6 czmdiver said:

Thanks M-8

Oh hey I see your in Perth.
 Get HOT there?
I was close to a Dive trip in western Australia to fly into Perth and drive north.
Some issue of driving at night up there with Kangaroo or Wallaby problems?
and some places seem to be closed during summer due to the high heat?Yes it does get hot in Summer.  Very hot up north.  Driving at sun down or sun up when the Kangaroos are feeding is the worse time, they jump in front of you when you are driving.  I don't know of any places that close over summer because of the heat. 

[nobodyspecial]

ok so I have put it back together. I got the 70cc kit.


I left the oil pump attached and have added premix at 45:1. It is only puffing a little bit of blue smoke out of the pipe so I am confident I am in the ball park. I have a new Mikuni carb with a 90 mains. The needle is in the middle. I ran 95 Octane. I am using Silkolene Scoot synthetic oil. I have a 8 heat range platinum plug from Scrappydogs. I was a little worried about the piston ring end gap of 0.20mm but I have no other option. I have a Malossi variator with 6gram 16x13 rollers and 1500 springs and contra spring. I gave it a quick blast up the street (after I warmed it up) and there are no flat spots and the acceleration is sharp and linear. I hit 75kph (45 odd MPH), it had more but I ran out of street. I wasn't kitted for a proper ride and didn't have all the bodywork on so I will get it together tomorrow. I also had about 25psi and need 41 in the tyres. I pulled the plug and there was no sign of overheating or should I say melting. I will do a plug chop soon and see how that goes.

[2stroked]

Aluminum versus cast iron for a 2t cylinder kit is an age old argument. Aluminum is great for race kits and expierience rider/mechanics. Cast Iron kits are great for mid race and Street set ups, and for people that are not as mechanically inclined as some.

Aluminum kits tend to be ported more aggressively, and need to be run a bit richer than a similar cast iron bore.


I am running a Polini Corsa with a Technigas and a 19mm round Mikuni with an 85 main. I have had that bike at a consistent 48mph. Not too fast, but it sits on 10 inch skins and has the useless thirteen something to one gears.



Aluminum kits are easier to ruin with an overheat, or a lean burn causing a soft sieze. Both types have their ups and downs. My cast iron kit has never gotten over 340 f. CHT. The stock iron 49cc bore ran that hit, at times a but hotter. Either type will give you miles if smiles if cared for and set up right.

[nobodyspecial]

Good stuff. I have a Technigas as well. I suspect anything over 80KPH with these will exceed the limits of the chassis and brakes so that will do me fine as a max. What do you think of my oil set up? i.e. pump plus 45:1 plus Silkolene Scoot oil?

[nobodyspecial]

Stuff me if it didn't cut out again after being on full throttle for about 10 seconds. I thought it had seized but started again (after about 30 seconds, first try) and I rode it home. Same old problem as before I reckon, it runs out of fuel somehow and somewhere!

[cyborg]

If you have an automatic vacuum fuel tap at wot the vacuum drop can shut them off,,had a similar problem with a Vespa et4,,ran great but kept shutting off at full throttle,,


As a side note I also changed the vac and fuel lines to clear from a local moto shop,,,makes hunting and searching into a quick look affair to see what's going on

[2stroked]

+1 on cyborg.

Sounds like a minor soft sieze or vacuum drop causing it to starve for fuel.

Using the injection pump AND a 45:1 mix is probably too much oil. If you are going to keep the pump, drop the pre mix down to about 50, or 60:1 plus the pump.

I honestly ran both for A SHORT while, and 50:1 was my max on the premix end.


Oh, check the reeds VERY closely, my ETon was acting odd, running uber rich for a few minutes then going so lean it would soft sieze or over heat. I can't guarantee the reeds were the issue, but after checking, then decking the cage and flipping the petals, it ran like a new bike.

[Alleyoop]

Usually the problems with the reeds is the petals get weak and do not close and stay open a little making them run rich so flipping them fixes that problem. I assume your fuel delivery is Gravity having the tank in back higher than the carb.

Make sure the fuel line from the tank to the carb is going down to the fuel inlet of the carb. No ups or downs as straight a shot as possible. Also make sure the tank is venting, in hot areas if the tank is not venting good it stops and or slows the flow of fuel from the tank.
You can try it crack the fuel cap open a little so it vents really good and run the sucker wot and see if it helps.
Alleyoop

[nobodyspecial]

Great thanks everyone, this is all very helpful, I'll tell you where I'm at.
I live in the most remote capital in the world (Perth, Western Australia) so I just can't go to my local shop and get stuff as they have no stock so I usually order off EBay and wait for the delivery (one or two weeks).

FUEL LINES
I have ordered a clear fuel line and will install that when it arrives. I took the vacuum hose off and sealed one end and blew from the other with the line under water. No bubbles no leaks. I paid particular attention to make sure it was completely sealed and fastened to the carb and the tap. I will unbolt the seat so if it stops I can quickly lift out the seat and bucket to check the fuel line.

PREMIX
I am only putting 500mL of fuel in a time so it is easy to make it 50 : 1. I will do that. At the moment I am witnessing blue smoke out the pipe which is reassuring, but not the optimum.

REEDS
I am running carbon fibre reeds. They have 1000 kilometres (625 miles) on them. I pulled the block out and held them up to the light and there are no gaps.

FUEL LINE ROUTE
Good point. I fitted an aftermarket fuel filter and in the process The line dips and rises (once), probably an inch to two inches from its lowest to highest "hump". I will fix this.

VENTING
I thought I had prepared for this by filing back the rubber seal around the cap but it still appears to have a strong seal so I will fix this. I didn't want an "open vessel" type situation say like a petrol can with the lid off as the petrol would loose its oomph and I have previously had trouble starting the bastard.
In saying that, with the 70cc kit and the new carb it is starting first go every time!

thanks again, stay tuned!!!!

[nobodyspecial]

FUEL LINE ROUTE
before:



after:




I did this before I rode it this morning. Usual story though, I rode for 15 minutes and she went snuffo at about 3/4 throttle this time.

So after I stopped I opened the fuel cap and took it off and it started again immediately.

[nobodyspecial]

I thought I had modified the cap enough to vent but I went home and put it on the grinder see below to try and get some air through.




Then I thought stuff it and drilled out a 3.5 mm hole through the top of the tank.




I then rode it for about 20 or 30 minutes daring it to stop on me. It didn't. I am not out of the woods yet, I will do more testing and plug chops but I seem to be on the right track now.

[Alleyoop]

In hot places it is very important that the tank vents good the fumes create a lot of pressure and stop or slow the fuel from flowing out.

Also Your Fuel Filter is Backwards, the wider part of the filter which is where the actual filter is attached to goes toward the carb. You want the fuel to be outside the filter being sucked through it. The other way it restricts how fast the fuel can get through because it is still in the line.
Alleyoop

[nobodyspecial]

I installed this today. I haven't had a chance to run it yet on the road. The fuel seems to trickle out of that tap slowly. It is hard to see in the line beyond the filter, even with the premix. I might try a different colour fuel.

[nobodyspecial]

Ok first run, 10 minutes she went snuffo again. It started straight away and I rode it home. I took the fuel cap off completely and went for another run. 10 minutes in she cuts out again. Again it starts straight away and I limp home. No full throttle cut outs this time just normal riding.
God tends to play cruel tricks on me. I have the clear fuel lines and the fuel isn't exactly pumping out. I took the new tap off to look for a blockage and found I had only about 100mL of fuel left in the tank. This is despite the gauge showing over half full. I now find the gauge only works "above" this mark. i.e. if I fill it, it will show full but it does not drop below just above half.

Almost running out tells me I am using way more fuel than normal due to the #90 mains, something I will have to get used to.

As the fuel tank was empty I experimented with 100:1 premix ratio (oil pump is connected as well). Interestingly the same amount of oil smoke is coming out of the pipe as it was when I was running at 45:1. At 100:1 (3 litres fuel, 30 mL oil) it idles a lot faster as well. (I am using 98 Octane this time.) I ran out of time but I think I will boost the premix up to maybe 60:1 and hopefully it will keep going this time.