Makes sense to me, most small 2 stroke engines I have seen(weedeaters, snowblowers, etc) run at least 50:1 if not leaner. Granted, there is a size, speed and performace trade off from small motors to a 250cc, but I can dig the logic...[img]i/expressions/face-icon-small-cool.gif[/img]

 

I see what you are saying. Less oil in the mix will make it lean gas[img]i/expressions/face-icon-small-blush.gif[/img]il, changing to a smaller main jet makes the engine run leaner air:gas. I suppose you still end up in the same dilema where if you go lean on oil you will lose crank bearings or rings (too much friction). If you go lean on the carb by using a smaller main, then you detonate and put a hole in the piston.

Both are still more expensive that changing plugs.

I guess the bottom line is to start rich and work your way lean until the plugs look the best.

Thanks for the good discussion.

 

I have an 86 250R as well. I run it at 40:1 on Bel ray MC:1 Think about how old our 250rs are and how far technology has come with 2 stroke oils. I was loading up too much at 32:1 so i went to 40:1 and once the 250R is warm it barely smokes. I would can the 20:1 mixture and leave it in 1986.

 

I too bought an FMF pipe & silencer for an 85 R that I just rebuilt. Bulldog, 85 had roundslide carb , 86 came with flatslide, otherwise same. I find I have no bottom end now although I never rode the bike before. I have played with the clip a bit but to no avail. I am going to put the stock pipe back on just so I have a baseline for reference. FMF website say jetting changes not needed although that is a general guide. I have no idea if a previous owner changed jetting so I will get it jetted right for stock and then try Pipe again.
Definetly go to 40: 1 mixture with good oil like Redline or Maxima
Brad
85 250
03 TLD Predator

 

Thanks for all the concurring opinions on the premix ratio debate. I am convinced that 22:1 is waayy to rich (although the lack of bugs around my house is nice [img]i/expressions/face-icon-small-happy.gif[/img]) I already ordered new oil and am looking forward to mixing up a fresh batch of 40:1 to see how the old screamer does on it. I never even thought about the technology despairity between 1986 and now. Good call Justin! Good info everybody for the premix debate!

The FMF pipe issues remains: I ordered some new jets and some carb parts (throttle valve was worn), I will try going up a main size or two to see if it helps. Right now the bike just kind of falls on its face until 1/2 throttle, then it picks up really nice- but no lowend neckbreaking "snap" when you gas it hard.

The fatty pipe is supposed to be a good all around power pipe- the power curve shown on the documentation shows an increase across the board, low, mid and high. I spent all day Sunday messing with needle positions, just made it run worse.

I remember how it rode when I brought it home- scary fast, the way the R is supposed to be the first time you ride it. Im sure once the tuneup is figured out it will run like a champ again. Thanks for the great info again everyone! Ill post complete results when I get parts in!

 

oh- either way, bad tuneup or not, my R beats the heck out of the old yamaha ytm 200k wheeler I used to ride- no suspension in the back- yyeeeooowww!

 

***Update***

Mixed up a fresh batch of Klotz R50 at 40:1, helped the smoke situation big time! Thanks again for the great info about premix ratios... [img]i/expressions/face-icon-small-happy.gif[/img]

Got a used 150 main jet from a dealer last weekend, dont think it was right though- not the same size body(the hole through the middle was obviously different... 3 bucks, never tore into the carb before, had no idea of size[img]i/expressions/face-icon-small-mad.gif[/img] ) Ran like *** when I tried it, but it did run. Ordering some new old stock jets from bike bandit today. Cant find anyone else locally who has any.

BTW- I put some pics up of my bike if anyone is interested- check my gallery

 

ok im going to make this fast. do you know what a plug chop is?

You should mess around with the pilot jet some also, and the pipe could have moved your power band up to higher rpm. And one thing to really get your bottom end alot beter with out spending money is to take the stock head gasket and split it up so theres 3 pieces and take ONE of the SMALL pieces and put it on and I garentee you will notic a big diffrence. (adds compression)

"PLUG CHOP"- is when you let your bike get good and warm and then put it in gear and go in the rpm range that your trying to get jetted in. In your case slow rpm (quater throttle) So put your biek in like 3rd gear or higher and go quater throttle for about 30 seconds and then pull the clutch in and shut it off. then check and see what color the plug is. If its black or dark brown, its to rich. if its white or a light color its to lean. rich= put a smaller jet in. lean= put a bigger one in. The perfect color is a tan to a paper bag brown...... NOW, if your trying to get your MAIN jet jetted right then put your bike in 3rd or higher and hold it to the bar for like 12 seconds or more. then see what color it is and go from there.

PlZ up date us when you have done soemthing.

 

Ill do a "plug chop" the next time I have a chance. ok maybe really stupid question, is a bigger jet a larger number? I assume it refers to diameter of the jet... Ive never had to jet a bike before, I dont know.... I hate asking dumb questions, but....[img]i/expressions/face-icon-small-confused.gif[/img]

 

When mine was stock with fmf fatty and silencer with K & N I ran 155,158 depending on weather. Not much variation. Bigger number equals bigger jet. sizes you should have 152,155,158.