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Post Info TOPIC: Rm 250 RESTRICTING


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RE: Rm 250 RESTRICTING
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I Was going to ask you how you've been getting on.

Make sure you get comparitor snaps of the barrels

I told you it's easy peasey :D

Keep going mate

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Its not going well :(

The powervalve and pump are quite technical, we dont really know what we're doing and my dad is concerned about setting up the timing, as in if we start it up and we've made a mistake the oil wont pump round and its fked

Gonna give it to a workshop guy we know to convert the parts over, need to do the valves on my kxf with him again anyway

Here's the comparison pics cal

image.jpgimage.jpgimage.jpgimage.jpg



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The exhaust port is enlarged so that's something, that will shift the band up. Are the transfers any different?

It's a two smoke? So it's premix oil. don't have to worry about oil pump failure?

Literally you're throwing money away if you give it to a mechanic mate, this job is designed to be done at the race track with the basics of tools!

Naturally if you're not comfortable doing it then fair enough, but there shouldn't be anything there that isn't taking it apart and refitting it. Have you tried looking at Youtube videos of how it should be done?

Anyway mate, I think this should tame the bike...slightly. It is a 250 two smoke after all, which is always going to be savage!

Good luck mate, keep us posted!


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Godamn i dont know thats what i thought he must have just meant the premix fuel in general, its quite involved there is allot of wierd little bits like one bit was wound in a certain way spring loaded and then the bolts tightened to hold it in position, well we've loosened and taken the bolts off, wound the cap out and the bloody caps just come flying off, there is no way we will know what position that it was in originally, we dont know what we're doing just trying to prise stuff out with a screw driver, now on the powervalve bit we can't get it to go back in flush, gonna end up braking something

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Dunno what the transfer ports are

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Fuel and air is inducted through the crank case or cylinder. Either way it ends up swirling around the crank before being inducted through the transfers. The transfers are what 'transfer' the fuel and air from the crankcase to the combustion chamber. They're the spline like ports located at the base of the barrel.

YES get stuck in mate.

What's the WORST that's going to happen.

It will be possible to readjust the powervalve in situ, i.e. once it's on the bike. So even if it is incorrect to begin with, you will still be able to manipulate it when the engines in the frame.

The exhaust port looks modified so I bet you that powervalve has been too!

It's important that you do this work yourself. If you do you will have a better understanding on how it controls the delivery of power. It will also allow you make adjustments to suit your riding style i.e. give you more bottom end.

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Is it something like this mate?

Seems fairly simple

All it's doing is moving the valve an inch or so. So you won't go far wrong on the rebuild. A quick Youtube search and there is loads of help there mate.



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Ah you see that cap in the background with the two philip screws holding it either side? Thats the spring loaded basterd that flew off

I will try doing some research on the internet try figure it out, cheers aswell

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Should have bought a manual Daniel!

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It will be alright. Worst case scenario he can take it to a mescamic. But there is so much material on the web I reckon he'll be just fine.

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Yo cal my mechanic (who just asked for a beer for doing it) is changing the stuff over to the other cylinder and he says the powervalve wont fit... What do you think could be the reason behind that? Ta

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It's the same cylinder so no idea mate.

The only thing I can think of is that it's a customised powervalve but that's unlikely.

I'm sure he knows his stuff but is he sure it won't fit.

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Its ok, turns out there is a bit of a burr, something to do with the liquid as it was being made just didn't get removed enough i dunno i'll ask my dad again, but he said his dremmel he has wont reach so he's got to take it to his mate to use a lathe... And i thought i was just gonna owe him a beer lol

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Wet and dry will also be enough mate. It should be very soft ally so no need to be too vigorous.

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I'll leave him to it, he's worked with my bikes in the past so

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I'm sure, but then he'd know that it doesn't need to be turned on a lathe.

I'm not trying to be funny or nout. Just that you could have done this yourself, learnt a lot from it and actually feel satisified know that you have completely dissassembled the top end and rebuilt it yourself.

It may be just me, but I know nothing about cars before 6 months ago. I knew nothing about DT's 3 years ago.

I work in IT, I'm not a mechanic. Never was any good at this stuff and it used to frustrate the hell out of me.

I jumped straight into my car. Completely rebuilt the head. All the valves taken out. Examined, lapped. New valve stem seals. Valve clearances measured. Cams polished. Head gasket cam belt etc etc..

When I drive my car there is a huge grin on my face. Not because I'm boosting it to the red line, but because I know I've built this engine that is currently reving to 7K. It's my hands that have assembled it. Okay it's Mr Toyota that built and designed it. But even so, there is something so satisfying knowing that you're driving something you've built. And I know you will feel the same when this is all said and done. Okay so the powervalve thing someone else is doing. But I know you could do it if you stuck at it. And you'd be so satisfied when you're ripping it round the track. Also knowing that if for what ever reason it decided to konk out. You'd have the confidence to strip it down and rebuild it.

As said, I say this because it was once me that couldn't do much. But after lots of forum research and some practice, I can now do it. I mean even on Sunday I was helping to fix my brothers YZ which is seized (pictures on the new forum) :D. Got to start migrating over soon!

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Yeh you are 100% right but even the mechanic was saying its got to be done properly and you've got to know what your doing if you know what i mean, i was going to give it a go but i couldn't find a video to show me, missed a fkin weekend of riding aswell pissing about on it it was just starting to wind me up i want to ride and to me there is nothing better to do, so sitting there working on it at the weekend is no good i would rather pay to get it done so i can ride

Its the impatient way but i just cant stand not riding, fks my whole week up, i feel lost lol

The thing is i just get annoyed doing it because like with my job, to me everything has to be PERFECT, if i see a speck of dirt fall in to the bottom end when the cylinders off i freak out, any scratch internally any fkin spec i just would rather not get involved otherwise once its all back together all i will think about is that little bit of dirt fking up the engine... Lol, even though i know all the stuff i worry about isn't doing any damage anyway, paranoid i guess

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But this is it. You're paranoid because you don't know what you're talking about.

The powervalve, it hasn't got to be done properly. As I said, it's a little piece of metal that is controlled by the actuator arm from the gearbox. It's not even like the DTR YPVS system mate. It's more like Rotax's RAVE system.

It is either open, or it's closed. All you need is to fit it. When the actuator is opened it opens the valve to it's 'fully opened' position. That's it. You just need to fit it. If you did it this one time. Learnt how to do. Yes you miss a weekend, that sucks. But the next time the engine goes pop, it won't take you five minutes. This is where you actually save time. You're back on the track then next week, unlike if you had to get someone else to do it on their schedule.

As I say on my builds, NO ONE, No mechanic, not even your dad, is going to be more motivated to get that bike running sweet as a nut as you will be., Because you're the one riding it. You're the one who wants to be there next week at the track. And that is why YOU will put in all your effort into making it sweet.

Believe me when I say that the powervalve doesn't have to be bang on.

Piston ring end gaps do. Piston to wall clearances do. Hell to some extent even the squish band does. But the powervalve can be out, not a problem. You are talking about a thou of an inch, if that, to get it to fit. I can't see casting flaws causing that much of an issue.

I'm not purposely being a dick. It comes naturally. What I am trying to make you realise is that you will always be more motivated than anyone else. If you take an engine to a builder, and a spec of dirt drops down the bottom end, you really think he's going to give a fck? If it's not detrimental, and you will never know, then I highly doubt he will care.

I see it all the time mate. My friends are mechanics and they are faily rough with customers cars because they're against the clock. And so long as the car is fixed, they don't care if it wasn't done how I would do it.

They are good mechanics and the last thing they'd want is a customer car coming back. But they don't care about the car, bike, engine or component. As said to an extent.

I'm just having a debate anyway. You do it however you feel is right. I was hoping you might give it a go and really get into all the intricacies of it all. But you've got to want to do it.

Because my car is a Japanese Import, finding work books in English just isn't possible. But it is the work of me practising with two stroke engines that has allowed me to fix it. Same rules apply, albeit with a lot more complexity.

I like engineering so all this fascinates me. I probably like building things more than I actually do using them. I think I've done 250 miles in my car since I've had it now. And it's currently jacked up off the ground with no wheels whilst I do some work to the undercarrige (can be seen on the new forum :D ) I could drive it, but I like fixing things.

Wet and Dry paper is not a copout for this job. I'd say a lathe is a little bit excessive, depends on what actually needs doing as your description is a little vague. Modifying the powervalve is a routine procedure that can be performed by amatuers, and I was once that person saying the same thing! I went to my mechanic who does the more technical jobs, crank rebuilding and balancing, and he told me it was standard procedure.

Best of luck anyway and keep us posted!

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You provide so much advice and knowledge i do really appreciate it mate, but turns out the mechanic had to do it anyway...

He said it had been caked in nicka seal (not sure how its spelt) basically what they relign the barrel with, all the ports were blocked with it, couldn't get the powervalve in because of it. Why would you need to relign a brand new barrel? It must be used, the bloke i bought it off just said it was new

Next, the original barrel on the bike is NOT ported or modified in any way according to the mechanic, totally standard all the guy had done was wind the powervalve adjustment screw in all the way so that the band kicks at the very top of the rpm's

So now i can adjust the powervalve accordingly using this screw

A fkin bummer, but i dont know who to believe...

Double whammy

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The barrel was replated. Don't worry about that mate. All you are interested in is a fresh barrel with a clean good bore. That's what you paid for, that's what you got so happy days!

Okay so whoever related the barrel did a poo job but that's cool your mechanic has sorted that out which is Great!

Nikasil is a electrostatic plating technology which hardens the surface of materials, like aluminium, so that you can run a piston against it and not destroy the barrel.

Sounds all legit to me me mate.

So it won't be far off now which is good.



-- Edited by Calum122 on Friday 26th of June 2015 07:07:12 PM

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Yeh, 70 down paid the guy for sorting it out took him a couple of hours but he persisted, but still tried to refuse the money when he handed the barrel back

We will put it all back together tomoz and run it in, then its canada heights next week!

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So the whole time your power mad bike could have been sorted by looking at the manual and adjusting the power valve! It'll be funny if this new barrel gives you more compression and therefore more power!

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So yes adjusting the powervalve would help on the bottom end but there is more to it than that. The fact the exhaust port has been enlarged says straight away that nothing you ever do to the powervalve will correct this. I'd expect that the transfers will have been altered as well, again emphasising that a new barrel was necessary.

The result of these modifications is not a direct increase in performance but a loss in rideability. Whilst it's true it will make more power, it also loses midrange torques which is what 2stroke was struggling with. By swapping the barrels over he will get back this torques and have a more tame, but still ruthless, bike.

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Well here she is, got it all back together this morning just riding it in, haven't opened it up yet but i will towards the end of the day, use to start first kick everytime and idle perfect but took multiple kicks and now wont idle? Does this prove that the cylinders were definately different? Thoughts

image.jpg



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Has it been jetted back to stock as discussed. You want stock jetting mate. Then you need to find out what they do from stock jetting to suit the aftermarket pipe!

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How did that bloody number board find its way onto your bike!

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Rmz front end conversion

Cal i just went counter clockwise 4 turns and it seems to have sorted it out, starts first kick and idles ok now

Now the bike... Man, what a difference. I was just chucking it around in the woods, the whole feel of the bike has totally changed, powerband kicks in mid range and just keeps pulling, SO much more torque and so much smoother, no snappy band just a really strong pull throughout the revv range

I did get a vid but i dropped my phone earlier and it didn't really get the sound something broke when i dropped it :( but it sounds nice and crisp

Taking it to the track tomorrow, gonna see how it feels and adjust the power band , can feel it might need to be tightened in a bit to move it a touch more top end but we will see, wanna set it up real nice tomorrow for canada heights next week, gonna be so sick

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YES MATE YOU DONE IT! I'm pleased for you and you should be proud. With a little help you've done a top end rebuild and more importantly you've fixed the problem yourself.

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Haha yeh cheers bud, just gotta tune it to how i want it now, got the kxf valves done and shimmed starts 1-2nd kick now, sell that for 1600-1700 put some if it into the rm

Might put up a gopro vid of tomoz

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