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red_russian1
05-06-2019, 09:27 PM
Good evening! About 6 years ago, I acquired my brothers 250R (the one in the pics). I stripped it down to the frame, rebuilt/repainted nearly every part and bored the cylinder out to about .070" over (I'm guessing because I don't recall off the top of my head). I also installed a set of Boyesen Pro Series reeds and Moose torque spacer. After I broke in the rings, I found a guy that was selling a larger carb off of a supposed '84 or '85 250R. I think I paid $40 but never installed it because I wanted to put a kit in it and I also would've needed to remove the air box and install a filter directly on the carb.
Well, 6 years later and after the trike has been sitting for 4 of those, I decided to dust it off. Choke is broken, right tire is flat and a mouse nest in the air box but it started after about 5 kicks!
So, my question is; has anybody installed this larger carb on their trike? I'm just looking for some info on what jets to install, air filter to use, etc. Thanks in advance!https://uploads.tapatalk-cdn.com/20190507/ed460b8876434c28092752758777be3b.jpghttps://uploads.tapatalk-cdn.com/20190507/df02fc493c45aeaaee1f2ae3e149e462.jpghttps://uploads.tapatalk-cdn.com/20190507/916d60f8ed5084ceae4aa335606123be.jpg

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yaegerb
05-06-2019, 11:21 PM
Yeah you can, may require frame mods but I have put a 41 TMX in an 83 before. Just need to take measurements. I would go with a modern carb like a keihin pwk or mikuni tmx.

red_russian1
05-07-2019, 12:10 AM
Yeah you can, may require frame mods but I have put a 41 TMX in an 83 before. Just need to take measurements. I would go with a modern carb like a keihin pwk or mikuni tmx.Modern because of parts availability? Will I notice very much difference with the one I planned on using?
I remember chatting with someone when I first got the bigger carb about which carb adapter to use. They said I should be able to heat the '83 adapter to stretch it over the larger bore and still be able to run the factory air box...

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barnett468
05-07-2019, 02:47 AM
I also installed a set of Boyesen Pro Series reeds and Moose torque spacer.

Why did you put the spacer in it?

red_russian1
05-07-2019, 06:26 AM
Why did you put the spacer in it?It's supposed to change the power curve to give it better low end. It does have tons of low end now but I think I might pull it out if/when I change the carbs.

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atc300r
05-07-2019, 07:20 AM
Its hard to do but posible.I stuffed a 38 mill carb with esr reed block 13 mill reed spacer and a DG intake in my 300r. Im using my stock airbox with lid removed.258424

barnett468
05-07-2019, 11:30 AM
It's supposed to change the power curve to give it better low end. It does have tons of low end now but I think I might pull it out if/when I change the carbs.


Well, actually, the majority of the time they REDUCE hp and soften then hit. They were originally designed for the 1978 YZ400's. These bikes and even my 1981 YZ465 have a boost port in the rear that is partially blocked by the reeds, which renders the boost port less effective. The 78 400's and the 80 465's also had a very abrupt power hit, so strangely enough, this spacer softened the power hit but still increased the power. It sounds a bit contradictory but that is what they did. I had a 1978 YZ400 in 78 (I also have one now) that I raced in the Pro class, and the engine was stock with the exception of an ANSWER silencer, and I was always an extremely good starter, but after I got this bike, I went from getting 1st thru 4th place starts, to getting 6th and 7th place starts against the same people, and when it came on the pipe, it would get squirrely, so I called Dave Miller, whom had a shop called Miller Mano at the time (now called DMC), and whom sponsored me in 1976, and told him what was happening, and he told me to get the spacer and install a 2 tooth larger rear sprocket, which I did, and the spacer reduced the abrupt hit so the bike was more controllable even though it now had a larger rear sprocket, and the very next race I got a 3rd place start and finished in 3rd even though my rear brake rod came off in the first turn, and every start and finish was much better after that.

Since the mold was already made for the spacer and the mfg still wanted to sell as many of them as they could, they simply gave it a fancy marketing name like "Reed Valve Tourque Spacer" which suggests that it increases an engines torque, even though it actually reduced hp on nearly every bike at the time except for the 1978 YZ400, lol.

.

atc300r
05-07-2019, 11:49 AM
On the 250r the reed block covers part of the ports .I use them on my aircooled 250r and 300r so the aftermarket reed blocks will and not bottom out.

red_russian1
05-07-2019, 12:02 PM
On the 250r the reed block covers part of the ports .I use them on my aircooled 250r and 300r so the aftermarket reed blocks will and not bottom out.So, leave it on?

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barnett468
05-07-2019, 12:37 PM
So, leave it on?

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No, you need to test it, so simply try it with and without the spacer, but I can guarantee you that if you are looking for a fairly noticeable increase in low end, the spacer will not provide it. Also, the rear boost ports still function without the spacer, and to improve their function a little, the bottom edge of the port closest to the cylinder can simply be radiused a bit to unblock them some more.

.

red_russian1
05-07-2019, 12:53 PM
No, you need to test it, so simply try it with and without the spacer, but I can guarantee you that if you are looking for a fairly noticeable increase in low end, the spacer will not provide it. Also, the rear boost ports still function without the spacer, and to improve their function a little, the bottom edge of the port closest to the cylinder can simply be radiused a bit to unblock them some more.

.Did you have any pics of how these ports should be modified? I might tear it back down someday to do it but at this point, I'm just looking at swapping carbs out.

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barnett468
05-07-2019, 12:57 PM
On the 250r the reed block covers part of the ports .I use them on my aircooled 250r and 300r so the aftermarket reed blocks will and not bottom out.

I'm not very familiar with this exact model but doing a quick Google search I found 3 cylinders that all sellers claim to be from an 83 250r and 1 has a boost port and it is red, and the others do not and they are black. Obviously the cylinders could have been repainted a different color but my bet is that the boost port cylinders are actually from an 84 and, and if so, there is no boost port for the reed valve to block in an 83 cylinder unless someone removed the bottom of it to open it up which I think is the case because I saw 2 82 cylinders that had the boost port.

.................................................. ...........https://i.ebayimg.com/00/s/MTE5NVgxNjAw/z/EvkAAOSwH9dZi-1u/$_12.JPG



The black cylinder

https://i.ebayimg.com/images/g/JycAAOSwFXdbqmY1/s-l1600.jpg

barnett468
05-07-2019, 12:59 PM
Did you have any pics of how these ports should be modified? I might tear it back down someday to do it but at this point, I'm just looking at swapping carbs out.


I do because I did the same thing on my 1981 YZ465 around 4 weeks ago but I will have to find them.

yaegerb
05-07-2019, 04:11 PM
Modern because of parts availability? Will I notice very much difference with the one I planned on using?
I remember chatting with someone when I first got the bigger carb about which carb adapter to use. They said I should be able to heat the '83 adapter to stretch it over the larger bore and still be able to run the factory air box...

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Yes, easier for parts and better technology.

red_russian1
05-07-2019, 10:18 PM
Yes, easier for parts and better technology.So, any idea which carb or size to run? I'm not really looking to dumping a bunch of $$$ into a new carb if this PE will work.

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red_russian1
05-07-2019, 10:38 PM
Yes, easier for parts and better technology.A flat slide 39mm for $100?! How do I know what size to look for? I think the OEM is a 30mm.

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https://uploads.tapatalk-cdn.com/20190508/4a1a2a520336bb7e10529bc26020d409.jpg

barnett468
05-07-2019, 11:07 PM
So, any idea which carb or size to run? I'm not really looking to dumping a bunch of $$$ into a new carb if this PE will work.



If the pe will fit, it will "work" as long as it is operating properly. As far as size goes, if your engine is close to stock, I wouldn't go larger than a 32mm. A new style carb won't do much for you other than drain your wallet.

yaegerb
05-07-2019, 11:10 PM
So, any idea which carb or size to run? I'm not really looking to dumping a bunch of $$$ into a new carb if this PE will work.

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Have to know more, I see a dg head, usually high compression, rod length etc. do what you want but you will be rebuilding that PE.

barnett468
05-07-2019, 11:16 PM
A flat slide 39mm for $100?! How do I know what size to look for? I think the OEM is a 30mm.

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https://uploads.tapatalk-cdn.com/20190508/4a1a2a520336bb7e10529bc26020d409.jpg

Waaaay too big.
.

barnett468
05-07-2019, 11:30 PM
Since you say it has lots of low end power now, if you want more mid and top end power and are willing to sacrifice a little low end power to get it, you can simply remove that stock 30 lb muffler and replace it with a straight thru type.

red_russian1
05-07-2019, 11:52 PM
Since you say it has lots of low end power now, if you want more mid and top end power and are willing to sacrifice a little low end power to get it, you can simply remove that stock 30 lb muffler and replace it with a straight thru type.I have a DG pipe/silencer on my wishlist but it probably won't happen until next year. I need to replace all 3 tires, rebuild the rear master cylinder and replace the air filter still. I'm not racing the thing but I do want to have fun on it when on the trails.

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barnett468
05-08-2019, 08:10 AM
I have a DG pipe/silencer on my wishlist but it probably won't happen until next year. I need to replace all 3 tires, rebuild the rear master cylinder and replace the air filter still. I'm not racing the thing but I do want to have fun on it when on the trails.

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Have you even ridden it on the trails yet?

red_russian1
05-08-2019, 10:45 AM
Have you even ridden it on the trails yet?Yeah I've taken it out a couple times, but not since about 2013 (we moved and it's been sitting ever since). Kick ass when coming up over a hill and pulling the front tire off the ground til the bottom of the dip!
I'm going to try and get tires ordered yet this month, along with the air filter (damn mice [emoji34]).

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barnett468
05-08-2019, 11:17 AM
Ok then it really might be best if you ride it again then tell us what you would like the engine to do that is different than what it is doing now before you go buying parts you may not need. You may also just need a different silencer instead of an entire expensive pioe to get the type of power you want so changes can be made in small steps one at a time to kerp from buying unnecesssry parts.

red_russian1
05-08-2019, 02:08 PM
Ok then it really might be best if you ride it again then tell us what you would like the engine to do that is different than what it is doing now before you go buying parts you may not need. You may also just need a different silencer instead of an entire expensive pioe to get the type of power you want so changes can be made in small steps one at a time to kerp from buying unnecesssry parts.Do silencers make that much of a difference, compared to the complete pipe? And does any else make them for the '83 besides DG? Dennis Kirk is the only place I've seen them.

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barnett468
05-08-2019, 03:33 PM
A strsight thru silencer typically makes a fairly noticeable difference compared to a stock silencer like yours which also has a spark arrestor and the aftermarket silencers thst pipe mfgs make typically fit both a stock pipe and their aftermarket one, in which case you can spend a smaller amount on the silencer first to see how it works before spending a boat load on a complete pipe system.

RubberSalt
05-09-2019, 10:10 AM
Your pipe and port work will determine what carb you need.

This is for a stock stroke+stock bore (or close too) 83 250r.
Trails = 32-34mm
Built/Dunes = 36-38mm
Drag racing = 42mm

The Keihin PWK like is very nice and easy to jet. Make sure you don't end up with anything Chinese. Those things will make you leaner than a vegan.

barnett468
05-09-2019, 10:57 AM
Drag racing = 42mm


I have never seen or used a 42mm carb on any single cylinder 2 stroke 250 no matter how much it was modified but I'm sure some people have installed them, but I would love to see a dyno sheet with the same type 38 vs a 40 vs a 42 on any model, but especially on an atc250r.

yaegerb
05-09-2019, 11:06 AM
I have never seen or used a 42mm carb on any single cylinder 2 stroke 250 no matter how much it was modified but I'm sure some people have installed them, but I would love to see a dyno sheet with the same type 38 vs a 40 vs a 42 on any model, but especially on an atc250r.

I am sure Selvy has some. Hit him up on facebook. We do it all the time to the air cooled 250rs. The last 83 I built for a customer was a 41 tmx taper bored to a 42mm. The customer here can feel free to chime in, but he would say that by the seat of the pants it was a completely different animal than with the 32mm.

barnett468
05-09-2019, 06:05 PM
I am sure Selvy has some. Hit him up on facebook. We do it all the time to the air cooled 250rs. The last 83 I built for a customer was a 41 tmx taper bored to a 42mm. The customer here can feel free to chime in, but he would say that by the seat of the pants it was a completely different animal than with the 32mm.

That's an idea, I will probably send him a message next week if I slow down long enough and see what he has for dyno sheets or see what he says and will post whatever he replies back to me with.

RubberSalt
05-10-2019, 01:31 AM
I have never seen or used a 42mm carb on any single cylinder 2 stroke 250 no matter how much it was modified but I'm sure some people have installed them, but I would love to see a dyno sheet with the same type 38 vs a 40 vs a 42 on any model, but especially on an atc250r.

All out high RPM monsters. At 9200 RPM with perfect porting for drag racing, looking for maximum power, 42mm is it.

The stock KTM SX 125 uses a 39mm PWK. Little bitty guy with a carb half the size of the motor. lol

barnett468
05-10-2019, 11:01 AM
The stock KTM SX 125 uses a 39mm PWK. Little bitty guy with a carb half the size of the motor. lol

Yes but you can't compare new technology to 40 year old technology. My 1980 YZ250 was the fastest 250cc production motocross bike ever made until the advent of the power valve engines that came a few years later, and my bike in stock form put out 32 hp. Mine has had some minor engine and pipe mods done so it puts out a little more than a stocker, so it's probably around 36 hp and I use the stock 38 mm carb. The KTM 125 puts out even more hp than my modified bike at 38 hp.

There was a newer KTM 125 in the same race I was in a few months ago, and I am a very good starter, and this guy blew by me and everyone else on the start and had around a 3 bike length lead going into the first turn, and I got a very good start and was in second, lol.

350for350
05-10-2019, 08:20 PM
Ok then it really might be best if you ride it again then tell us what you would like the engine to do that is different than what it is doing now before you go buying parts you may not need. You may also just need a different silencer instead of an entire expensive pioe to get the type of power you want so changes can be made in small steps one at a time to kerp from buying unnecesssry parts.

I have to agree with this here. A couple of years ago, I rode a 1981 250R. Not long, just enough to get a feel for it. After yeagerb completely rebuilt the engine, ported it out, and the owner put a full DG exhaust on it (I have no idea what type of carb was on it), it was an entirely different machine, and it felt like it had almost twice the power. It was amazing engine work. I told the owner that while it was great, I'd actually prefer it stock for 90% or more of the trail riding that I do. It lost bottom end power after all of the mods. I usually ride tighter trails and not at race speed. It may just like Barnett said, you may not need many parts for it to run like you actually want it to. It's easier to modify your trike than it would be to put it back to stock, assuming that you have some serious engine work done.

JacobMonster
05-10-2019, 08:27 PM
Honestly, I wouldn't think the DG would make that big of difference in the power. I have an 82 with a DG silencer and stock head pipe, with stock jetting I assume. The thing rides the same way you described your stock 83. Beastly low end, lift the front wheel anytime you tell it.

With my woods build that I'm slowly working on, I'm just going to run the stock carb with a full DG. I'm just buying the header pipe because I have the DG silencer and my stock header is bent, so it leaks exhaust right at the engine. I want to run a Lectron carb on it. I've heard so many great things about them. You don't have to jet the carb, it does it automatically. But you pay a pretty penny. I think they were close to $500.

I say if you want something good for the trails and low on cash, keep the carb you have and fine tune it. No sense in going through the hassle of making a carb fit and all that jazz unless it will significantly change the performance of the bike. You could do more by simply changing your gearing than messing with carbs.

barnett468
05-10-2019, 10:06 PM
I want to run a Lectron carb on it. I've heard so many great things about them. You don't have to jet the carb, it does it automatically. But you pay a pretty penny. I think they were close to $500.


Actually, contrary to the few positive reports there are out there about them, there is a very good chance you will have to "jet" it like many other people have, which may very well involve replacing the needle with another one, which consists of calling Lectron and telling them exactly what the problem is etc and then having them take their BEST GUESS as to which needle will work best, and if it still has a problem with the new needle they send you, you are back to square one.

Do not believe the advertising/marketing hype and make the mistake that this extremely expensive carb will bolt on to your bike and work flawlessly. imo, if it does, you are extremely lucky, and if it doesn't and you have to start changing needles etc, you may be extremely unhappy.