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Old 02-14-2015, 04:07 PM   #1
Frey OP
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Frzdy 440 (dr350 + yzf250f)

Hi!

I want to put a DR350 motor with a 90-92 DR250S 5th and 6th gear with a 440cc piston into a YZF250 frame.
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Old 02-14-2015, 04:15 PM   #2
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Here are some threads that lead me to this: Five speed vs six speed http://www.advrider.com/forums/showthread.php?t=281742

A lot of the manufacturers make the transmissions short so you have a better 1/4 or 0-60 speed.
I believe reviewers should start including an RPM @ 75mph rating. If magazines and websites started to post this in the 'specs' section, it would start to be something manufacturers would consider. In this regard, the TE610 really seems to be the only bike built with an open mind.



Of course I've seen Mondo Enduro. Then I read
Distech's DR 350 http://advrider.com/forums/showthread.php?t=528784
and Pablo's DR thread http://www.advrider.com/forums/showthread.php?t=620198

The lightweight air cooled DR 350 has 6 speeds. Weighs 220-260

What's even better is the 90-92 DR250S has a granny gear where the 5th gear is as high as the other years 6th gear, and the 6th gear is higher than that.

Here are the gear ratio's by model:

Gear RatioDr250Dr250s 90-92
Dr350Dr350s
1st29/12 (2.416)29/12 (2.416)29/12 (2.416)

29/12 (2.416)

2nd26/15 (1.733) 26/15 (1.733) 26/15 (1.733) 26/15 (1.733)
3rd24/18 (1.333) 23/18 (1.277) 24/18 (1.333)24/18 (1.333)
4th20/18 (1.111) 21/21 (1.000) 20/18 (1.111)20/18 (1.111)
5th20/21 (0.962) 19/23 (0.826) 20/21 (0.962) 20/21 (0.962)
6th19/23 (0.826) 17/24 (0.708) 19/23 (0.826) 19/23 (0.826)
Final Reduction49/13 (3.769) 48/13 (3.692) 47/14 (3.357) 43/14 (3.071)



The DR is old technology, the suspension isn't top of the line anymore, the swing arm is like [ instead of []. Pablo addressed a lot of these issues in his build but still complained about the frame in general.

So my goal is to have the modern suspension of a lightweight dirtbike, combined with the lightweight and reliable technology of a aircooled engine.

This build will have an emphasis on being user friendly, safe, and dependable.
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Old 02-14-2015, 04:40 PM   #3
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Last week I got a great deal on a 1998 DR350SE. This bike has the better suspension, pumper carb and exhaust. Was fast and fun. This made me sure I was on the right track. Electric start. It doesn't fit into my build though. I sold it and bought a 1990 DR250S and a '05 YZF250 that needs a new crank.

This decision was based on something Pablo pointed out to me in a private message, the fact that both of these bikes have oil in the frame, something I will take investigate and photograph as I finish stripping down the Yamaha.

The DR250 will be my daily driver so I want to find a cheap DR350 bike or engine, that way I can get the YZF frame modified to accept a DR motor before I split the cases to take out the 5th and 6th gears. Hopefully the DR350 has the automatic decompression. Did they make a kick start only with this?

This bike will be a work in progress I'm sure and I want to do it as cheap as possible using as many parts from the bikes as I can and selling the rest.

From the DRs I plan to use
Instruments, wiring harness and key
350 motor as it has larger valves than the 250, eventually with 440cc big bore and possibly other modifications
250S 5th and 6th gears
Carb to suit the DR motor, possibly from a CRF150R
Cush drive 18" wheel from the DR250S

From the YZF250 I plan to use
Modified frame
Suspension front and back
Front brakes and Front wheel
YZF rear brake master cylinder connecting to one of the two rear brakes that works best for the DR's rear wheel

I can sell now from the YZF
Carb
Radiators
Motor
19" Rear Wheel
Controls
muffler



Things I will need to make or source
Headlight. The DR headlight won't fit over the forks. I'd like a round headlight that uses an H4 bulb such as the cyclops motorsports rally light (but im not paying 400 bucks)
Either reinforce or replace the very light YZF subframe. I will want to take passenger occasionally I want a lightweight rack. This will also affect what airbox and seat I use.
The YZF seat will not be comfortable
The exhaust I've thought about making a custom header that goes along the bottom of the bike similar to dakar bikes



but really my inspiration comes more from Tokyo motorcycle culture, you see these everywhere


I like in this photo how the rear end is minimal but they've kept the airbox.

The advantage of doing this, in addition to keeping weight low, is that you can clean up the rear end and keep the heat away from your passenger.
The disadvantage of this is of course your muffler gets hit by rocks when you're in the mountains of Colorado.
I think this mod will really come down to have much the mufflers I have on hand will bolt straight on and how much modding will leave room for creativity. The oversized header for the DR is 1.5" OD as apposed to the stock 1.375" OD.
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Old 02-14-2015, 04:50 PM   #4
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Pictures








oil dipstick in YZF frame



the frame is solid, I thought it was double cradle frame, it will be harder to modify, I will measure the two and post results. If you look at the water pump where there is small piece of armor, behind this is where the oil pipes are routed. I'll need to remove the motor to inspect.

Here is a diagram for the DR



It might be necessary to use an oil cooler or something similar to make the oil lines go the right way. If someone can find a diagram of the oil routes for the YZF that'd be great.

06+ the YZF uses an oil tank instead of having oil in the frame



There is nothing to this subframe. Will need supports, I want to be able to carry a passenger so I need a place for foot pegs, plus some bags for camping and general use.



i guess the seat is the air box door... nice big filter



everything came out well, only two stripped bolts. front brake lever and one f the subframe bolts. this is the most modern motorcycle I've worked out. its great there are so many of these half moon shaped bolts so you don't need to put a wrench on each side, plus you know how it goes back together.



I need to compare this to the DR350 swing arm pivot bolt. It would be great if this is similar.



This bearing has failed



This is how far I've gotten. The left side shows the stuff I'm planning on keeping and the right is to clean up and sell. I need to clean out the shed so I can work indoors.

Any feedback or suggestions would be greatly appreciated. I've never done a project like this so even simple things like fitment of the motor, motor angle, mounts and other problems to look out for, please share!

Thanks
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Old 02-14-2015, 05:30 PM   #5
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Here's a DR350 motor in an RM250, Photos are from an inmate, sorry I don't remember who.

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Old 02-14-2015, 08:36 PM   #6
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The 94-99 DR350 dirt model is kick start only with the automatic decompression exhaust cam.

The DR engine isn't fit between the swing arm pivot like the Yamaha engine is, so there is another problem to solve.

I like the concept, but it's going to be a lot of work if you can make it happen. Looking forward to seeing some progress.
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Old 02-15-2015, 11:16 AM   #7
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Quote:
Originally Posted by tntmo View Post
The 94-99 DR350 dirt model is kick start only with the automatic decompression exhaust cam.

The DR engine isn't fit between the swing arm pivot like the Yamaha engine is, so there is another problem to solve.

I like the concept, but it's going to be a lot of work if you can make it happen. Looking forward to seeing some progress.

Thank you, so the next step is getting one of those DRs

I took a look at the DR, I think I can weld a spacer to the YZF frame to take up the space of the motor, and then tabs to bolt the DR motor the way its mounted in the DR frame. I hope I don't have to move the motor too much to clear the spacer. It will be easier to tell when I get a motor.

A comparison of the oiling systems...









You can see here the part of the frame that holds oil. I believe that hose goes to the head. I will have to inspect it more and see if there are any arrows or find a service manual and compare it to the DR350.





EDIT: I added these comparison pics of the DR on 2/27/05 to keep the thread tidy. These look pretty similar. The oil pump is in the motor, the frame is just passageways, is there any reason why these pipes shouldn't be just a straight swap? One issue I foresee is that the oil is added to the motor of the YZ and to the frame of the DR, so i'll have to figure out how to put oil into this thing

Right now I'm trying to clean up parts to sell and get out of the way.

The YZF250 motor with no oil only weighs 45lbs!! It would have two radiators and all that weight but still! feather weight... It sure is tiny.

Some data collected:
Dr350 Kick only is 77lbs
DR350 E start motor 83.5 lbs
Kawasaki Ninja 300 91.8 lbs
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Old 02-15-2015, 06:06 PM   #8
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I'd keep that YZ carb, I think it's the FCR37? Could be tuned to work really well with the DR engine, especially if you big bore it.
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Old 02-15-2015, 06:24 PM   #9
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SG350 (DR350 motor in a street frame) has an oil cooler and holds the oil in a tank under the motor. I think this bike is super rare so probably not many parts available. I bet there is some cool stuff that could be used



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Old 02-17-2015, 02:33 PM   #10
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Now looking for a 1994+ DR350 engine for the auto decompression head

meanwhile, getting the YZF frame street legal
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Old 02-17-2015, 03:39 PM   #11
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I think you can do it, but it's gonna take some time and work and money. A lot more than you think. Getting the motor sprocket as close as possible to the swing arm pivot is important to keep the chain from chewing on the swing arm, also keep an eye on chain/sprocket alignment. A good mig welder is nice to have. I have a tig but the "torch" is a little hard to get into tight spots and the foot pedal can be awkward at odd angles. Also you may want a big compressor and a couple of small die grinders with cut off wheels and abrasive discs and a 4" electric angle grinder with cut off wheels and flapper wheels. HF is a good source for cheap ones.
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Old 02-17-2015, 06:47 PM   #12
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your off to a good start. good luck with your build. I have not read your post completely yet so if I missed something you mentioned I apologize in advance.
if that yz came with a fcr37 like I assume it did you should use it. I put a fcr37 on my 441 and it is a great choice. much better than the pumper that the dirt model came with.
I am assuming your wanting the auto decompression cam because most of the forum members say its easier to start. I used to believe that but in my experience auto cams are much more finicky to start and really do not like cold weather. the cam is robbing the engine of compression to make it easier on you. good compression makes a bike start much easier. my non automatic decompression bike will ALWAYS start. if your smart about it and use the decomp lever its a piece of cake.
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Old 02-18-2015, 05:23 AM   #13
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Quote:
Originally Posted by 2bold2getold View Post
I think you can do it, but it's gonna take some time and work and money. A lot more than you think. Getting the motor sprocket as close as possible to the swing arm pivot is important to keep the chain from chewing on the swing arm, also keep an eye on chain/sprocket alignment.
Thank you.

These are the things I'm most concerned about and why I need to find the engine to move further. Most of this trouble comes from the fact that the DR engine will have to sit further forward than the YZF250 engine because of the way the swingarm does go through the YZF engine but goes behind the engine on the DR.

As for alignment generally is it better to move the engine off center in the frame or the wheel or both?
Since rear wheels use spacers and I'm using the DR250 for its cush drive,
Could I help align the sprockets by having the wheel slightly to one side or the other or is this super bad?

I used to work on bicycles and fixed gears, converting road bikes with multiple chain rings to single chain ring up front. We always worked for a chain line being straight. But seeing as humans produce 2.5hp - .1 its not really the same

Quote:
Originally Posted by brownvv View Post
your off to a good start. good luck with your build. I have not read your post completely yet so if I missed something you mentioned I apologize in advance.
if that yz came with a fcr37 like I assume it did you should use it. I put a fcr37 on my 441 and it is a great choice. much better than the pumper that the dirt model came with.
I am assuming your wanting the auto decompression cam because most of the forum members say its easier to start. I used to believe that but in my experience auto cams are much more finicky to start and really do not like cold weather. the cam is robbing the engine of compression to make it easier on you. good compression makes a bike start much easier. my non automatic decompression bike will ALWAYS start. if your smart about it and use the decomp lever its a piece of cake.
Thanks, I was wondering if you needed to bigger intake valves to take advantage of the bigger carb?

From DisTech's thread:

MFG______________VALVE LIFT__DURATION
Stock______________.328/.328__226/226 @ 0.040"
Web Cam 223_______.335/.335__240/240 @ 0.050"
Megacycle 31705____.372/.372__236/236 @ 0.040"

The stock valves are 30/27. New seats and new Kibblewhite valves will be 33/30.

Is there a rule of thumb with valve size in relation to carb intake size? I know this would factor in more things like flow rpm and compression etc etc

Id rather put the stock engine and carb in the YZF frame than wait till I have everything. In other words, if the FCR37 sells on ebay it's money for the build and I can just buy another carb in a year or so
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Old 02-18-2015, 06:36 AM   #14
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I am using non cush wheels on my 441 and see no issues as of now. might be allot easier to use the yzfs rear wheel. the 19 will also help keep your steering geometry .

how much oil does the yzf hold in the frame? I would guess its much less than the dr because the yz was a water cooled bike.

I would highly recommend the fcr37. it does not wear out like the tm33 pumper carb. the tm slide sticks to the throttle body and has a jarring effect when it finally let go on deceleration. the fcr is a smooth as silk because it uses a roller system.
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Old 02-18-2015, 07:26 AM   #15
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o and your a bad influence! I found an 04 yz250f with a title and a bad motor for 600 bucks and I am having a hard time talking myself out of it.
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