Jetting 36mm carb EXC200? JD jet kit

[Reckless]

I'm not saying its not possible, the theory is correct, but I did say "wouldn't OFTEN arise"
Jeepers we are talking about an old radial finned, air cooled, cast iron bore, round slide carb PE400 that blew up. Compared to our nikasil bore, water cooled bikes. Carburetion has come along way! Also oil technology is light years better. Those guys probably used the old castor based Castrol R.
Secondly you'd have to be in a low gear using engine braking alone with clutch fully engaged for long period of time. Hehe there's that word "Long" again. LOL!

The situation described would have to be not very technical either to be using engine breaking only for such a long time as to lean sieze it.

The fire breaks behind Whitanga where very steep I found that moving to 3rd or 4th was best. Kept the engine ticking over, with little load on it, without locking the rear. Bit like engine induced ABS. When you did lock it with the brake and it stalled it restarted really easy as soon as you released the brake. If you did feed it a bit of gas it didn't want to take off on you either.
Dunno if thats the correct method but it seemed to work OK??

A bit of fuel now and then never hurts and I usually go with the flow but you can't convince me on this one.

[warewolf]

I'm not saying its not possible, the theory is correct, but I did say "wouldn't OFTEN arise"

"Often" is one of those words, too Several times each lap for 2-3 hours could count as "often". The terrain here is nothing like say Woodhill. The biggest downhill I know in there is less steep and quite short, only 1- maybe 200m.

Secondly you'd have to be in a low gear using engine braking alone with clutch fully engaged for long period of time. Hehe there's that word "Long" again. LOL!

The situation described would have to be not very technical either to be using engine breaking only for such a long time as to lean sieze it.

They usually aren't very technical, apart from the steepness and lack of high-speed run out at the end, ie an almost-stop hazard so you can't just blast all the way down because you're gonna have to stop on the steep stuff. I do a mix of things, like you suggest with the higher gears and a little throttle, or clutch lever in all the way and brake... different things. Steep enough that you don't want to reverse a worn rear tyre because the lack of braking (or even downhill rolling) grip is highly noticable.

I am very intrigued by all this, especially your comments about modern engines. My 200 has been run on 40:1 premix, but I'd like to go 50:1 for less pollutants and less oil consumed. KTM says 40-60:1 depending on oil quality. Many people I've spoken to have more experience with road racing, they get the horrors even at 40:1, running 32:1 or 25:1. The reason for the latter is so they can safely shut the throttle at the end of the straight while braking into that 1st gear corner. If I'm going to go through the process of thoroughly checking and setting the jetting, I can change the oil ratio at the same time.

[Reckless]

I must say my opinions are my opinions only, you can all either take them or leave them. My experience has been in the Karting world Mainly with water cooled 125 engines on Petrol, Avgas and methanol, a few years ago now, but in the water cooled/power valve era. I have no formal mechanical or engineering qualifications. If you think what I say makes sense try it, if you don't, don't bother. Its only words on a forum!

"Often" is one of those words, too Several times each lap for 2-3 hours could count as "often". The terrain here is nothing like say Woodhill. The biggest downhill I know in there is less steep and quite short, only 1- maybe 200m.

I suppose it all boils down to common sense in the end!
I just didn't think it was a valid comparison blowing the PE400 to having to be careful on the tracks we ride here in Auckland on a 07 Ktm200. Camchain can be a bit over cautious as well?

I am very intrigued by all this, especially your comments about modern engines. My 200 has been run on 40:1 premix, but I'd like to go 50:1 for less pollutants and less oil consumed. KTM says 40-60:1 depending on oil quality. Many people I've spoken to have more experience with road racing, they get the horrors even at 40:1, running 32:1 or 25:1. The reason for the latter is so they can safely shut the throttle at the end of the straight while braking into that 1st gear corner. If I'm going to go through the process of thoroughly checking and setting the jetting, I can change the oil ratio at the same time.

We had karters running 60:1 (even me) with very lean settings etc. Even the dyno showed these settings to be quite good. But when on the track trying to push your fat butt out of a corner it just felt thin. Fine on the perfect race line & rev range but try and pass someone or make a mistake and it showed. I also read many reports/tests on high performance 2strokes back then and they all came to the conclusion more oil = more HP. I would hazard to guess this added up to better ring seal and therefore the piston was driven harder at each stroke developing more power. 25:1 did seemed to be the magic number as well. I personally don't think lean means mean in a 2 smoker.
In saying the above my 08 manual says 60:1 and doesn't mention any richer mix. My carb settings aren't to far away from the book so over all I suppose I'm quite rich. But it feels good, doesn't foul plugs, pulls like a 14 year old school boy & goes better than I can ride it, so I'm happy. I could probably go 50:1 as it is, but its only 5ml per litre I rather put that in and do less reconditions.
There's something to be said for not always changing things and just riding so you really get to know where it excels. We found this with our kids when karting. Take them to the track with the same kart for a few weeks and they got faster and faster, keep changing weight distribution, seat position etc etc to make it better and they never really got the hang of it. Hehe some fathers out there spent the whole time chasing the elusive "perfect" set up. We just smiled and beat them. Sooner or later you get faster by being fast yourself not by making the machine different everytime you get on it or blaming it.
Just my 2c??

[kezzafish]

Very interesting read, i've been following closely and have learned a lot from your discussion although it's all theory to me at the moment as i've never had a carb to pieces but i think i'm in a better position to have a hack if the need arises.

I had to pipe up and post something now cos' of your last comment reckless. I totally and whole heartedly agree that you must at some point just ride it as it is. It takes a lot of riding before you'll know exactly what adjustments will have a positive effect anyway. I've almost gone full circle with my suspension fiddling and although i learned something from it (which i believe is invaluable)... i basically ended up where i started.

Anyway cheers for the info and carry on regardless

[cheese]

There's something to be said for not always changing things and just riding so you really get to know where it excels. We found this with our kids when karting. Take them to the track with the same kart for a few weeks and they got faster and faster, keep changing weight distribution, seat position etc etc to make it better and they never really got the hang of it. Hehe some fathers out there spent the whole time chasing the elusive "perfect" set up. We just smiled and beat them. Sooner or later you get faster by being fast yourself not by making the machine different everytime you get on it or blaming it.
Just my 2c??

Couldn't agree more. Its funny you know, my bike has a few differneces to Sams CR and I found his one just strange to ride. But yes I think that if you're bike runs more or less fine, you will adjust your style to suit. The pros will know what a minor change in jetting would make, but as for average joe like me, if it all goes well, I just ride it (when I can!!)

[camchain]

Thread getting bloated - my fault for raising the seize Q. Good interesting subjects need new threads.

Yeah, the old PE400 seize-up is from a different era but mainly just an example to illustrate my Q. The only ride I've been on recently where I felt it might be an issue was the last 'A' option at Paparimu ride (the Mr Motorcycles one). Steep and very long. I just did pretty much what Werewolf described, quick clutch in and a throttle blip every now and then. Doubt much chance of a seize but just thought would be good insurance against extra wear from a dry bore, hot piston. As mentioned, being in the right gear has to be a good thing, no point in having the thing riiiiing-dinging all the way down.

Premix ratios - Reckless, I noticed the KTM ratio change in '08 and found it interesting. Maybe a political move for more environmentally friendly product?

The business of how much to tinker with a bike is a very good subject. There's definitely a lot to be said for the 'get things working and ride it approach.' I'm unfortunately in the 'always trying to improve stuff' side of the fence, and I love a well set up bike. Think I got this way from being an apprentice in a machine shop where accuracy was everything.

[warewolf]

I also read many reports/tests on high performance 2strokes back then and they all came to the conclusion more oil = more HP. I would hazard to guess this added up to better ring seal and therefore the piston was driven harder at each stroke developing more power. 25:1 did seemed to be the magic number as well.

IIRC that was raised too - same reasons stated. Maybe I'll just stick to 40:1.

There's something to be said for not always changing things and just riding so you really get to know where it excels.

You haven't been talking to Mick Doohan, have you?? He puts a lot of his success down to his ability to tell the Honda development guys to eff-off, that he wasn't a test mule. He reckoned he could beat everyone with the equipment he had. If a lesser rider beat him by using a new development, Mick would then take it up. He even went back to the inferior screamer engine to mind-fuck the opposition, and they took the bait and wasted testing time trying to use that instead of concentrating on the better big bang engine.

Thanks for the input Reckless, very helpful.

[Reckless]

Looks like we are pretty much on the same page really.
Very interesting the road boys came to a similar conclusion to us karters re Hp Vs oil mix and carb settings. Never knew that before.
If anything later oils are thinner and more slippery. Maybe we c should be using even richer mixes seeing as how we are not using the old thick oils??
When on Methanol I used Castrol MSSR which is pretty much straight Castor oil. Still have 4 litres in a pack here.
Smells good in the mower!

Mick Doohan I wish I'd seen him race!

[dammad1]

Premix ratios - Reckless, I noticed the KTM ratio change in '08 and found it interesting. Maybe a political move for more environmentally friendly product?

Exactly, be careful listening to the KTM manual when it comes to the mix ratio they are publishing these so that the bikes can meet the euro 3 emission regs, but that does not mean it is the best ratio for the long term health of your bike. I run 40:1 to be on the safe side and she runs sweet, changed piston at 86hrs and everything was mint.

[Reckless]

Exactly, be careful listening to the KTM manual when it comes to the mix ratio they are publishing these so that the bikes can meet the euro 3 emission regs, but that does not mean it is the best ratio for the long term health of your bike. I run 40:1 to be on the safe side and she runs sweet, changed piston at 86hrs and everything was mint.

Agreed my friend!! As stated, I run 40:1 as well. More oil more horse power Interesting why you think they went 60:1, market pressure aye! Probably for the USA regulations as well!

Cheers mate hope you don't go to Aussy though!! To many bloody aussies over there.

[dammad1]

Agreed my friend!! As stated, I run 40:1 as well. More oil more horse power Interesting why you think they went 60:1, market pressure aye! Probably for the USA regulations as well!

Cheers mate hope you don't go to Aussy though!! To many bloody aussies over there.

Yeah that is the only problem with oz, LOL but with the amount of kiwis going over there we may just start to take over.

[warewolf]

Mick Doohan I wish I'd seen him race!

Used to watch and listen lots; spent 3 days trackside at Eastern Ck then the Island each year. Worked across the motorway from Eastern Creek Raceway, could hear the bikes during the January tests etc in some offices (through the air-con ducting) and in the "beer garden" of the cafeteria. Was standing against the fence at the hairpin when he got t-boned by Criville... that move hadn't been possible for 25 laps, and nothing changed on the last one... Criville simply rammed him.

Doohan used to practice like he raced; balls out. Do laps on this bike, then swap bikes and do more laps on the second bike while they changed stuff on the first one. Repeat. Then he'd come out and do full race distance at race pace to see how the tyres would last. Everyone else used to piss and fart around, do a few laps, rest 10-15 mins, do a few more, tour around parts of the track etc etc. He certainly put the work in and earnt every win. I think there's a lesson there for all of us!

It helped that he held the throttle open further and longer than anyone else (easy to hear during practice), put the bike sideways more and laid bigger blackies.