I never intended to make this a build thread, but after thinking about all the awsome builds I have enjoyed reading about on here I decided to do it. Maybe it will help inspire someone else.
I have been toying with putting a Yamaha Blaster engine in a modern frame to create a low maint, light and fun play bike for years. Was leaning towards a 125 from the early 2000s to work with or possibly a 250f. I then came across a yz125, a kx125 and an xr250 with blaster swaps on the net and decided to do it. I knew the yz would prob be the easiest to do cleanly so I started looking for a basket case bike or roller about a year ago but people either wanted to much money or I missed out on a good deal by hours. Then one of my longtime friends mentioned he was selling his 2006 CRF250R. And so it begins, I had my bike!
He bought this bike as a basket case, pretty much rebuilt the whole thing and raced enduros and hare scrambles for prob 5 or 6 years winning his class the last year he rode it. It has sat partially disassembled for the past 5 years or so in his basement. Despite being tired after a full season of A class racing the bike ran great! After I fixed (or thought I did) a sticky front brake caliper I took the bike for a couple of 45 minute rides in the woods and old gravel pits near my house. I have never ridden this vintage CRF and after only minutes immediately felt comfortable on it. He always said this was the best handleing most forgiving bike he has owned and I see why, this thing is great in the woods! Even on old dry tires this bike felt very planted and stable and I quickly was pushing it pretty hard. I think im gonna like this thing. On the second ride the front brake started acting up so with that and a weeping radiator I headed home and parked it.
A few weeks later the teardown begins.
After stripping it and doing a quick cleanup I test fit the engine in the frame.
At first glance ill need to notch the frame for the right engine case and lightly grind the right side of the casting near the right footpeg and obviously cut out the Y. It turns out there is a lot more than that to do to get it to fit correctly. I will get into that in a thread update, but just going to get this thread started up to near where I am now and go into detail about how i dealt with each issue.
So i notched the frame and cut out the Y. Was gonna use a cr250 or cr500 engine swap casting for the Y, but no way that will work.
Gotta get the front down a ton to make it sit rite. Also the bottom engine mount will take some creative work to use because it sits so far back.
I cant bolt it through the frame because it sits almost touching the casting. Will document how I got around that in an update.
I got the chain aligned and cut and welded tubeing to the swing arm spacers.
So after a bit more work I ended up with this.
I had to do weld overlays on the frame where your boots rub it was paper thin. I built a Y out of 6061 tubeing and thinned the downtube on the engine side to get the engine sitting correctly. I welded and blended the grooves in the frame from the radiator shrouds, cleaned it and the swingarm linkage up and added these frame protectors. All of the linkage bearings were good and were cleaned and repacked. I had to replace one seal on the swingarm pivot that was a bit worn but that was it. I will go into detail about the Y and some other stuff and do a better job of documenting my progress in the future. Also go into detail about the engine and what is done to it. This bike will have a home built led headlight and I still need to mod the pipe and am working on some other mods. I also have a really nice set of 08 triple clamps and a honda damper to go on it. If I dont like it I can always put the 06 clamps back on. I also repaired and flame treated and painted a couple sets of old plastic IT blue. I will test the durablity but it looks promising. 2K clear is some pretty tough stuff so we will see. My goal is to be done before the end of September.
Before i stripped it I test fit some plastic to it. I think it will look good with some black excel wheels....
This is so impressive. I'm really interested to hear about how this thing performs/handles.
With the rear lower mount, I assume when the engine is positioned to attain the correct height of the CS to the SA pivot ( an Important Thing that I Know I go on Ad-Nauseum about , but, it's a Conversion Stuff Up So Many do ) a Bolt would be pretty much in line with the cradle tubes?
Now, perhaps you can put in mounts welded to the cross brace ( that the linkage goes to), and, put a 'port' on one cradle rail to feed the bolt through. Not hard, and, done well, strong.
Another 'take', is, to use Right Angle mounts, that you may be able to bolt onto that cross section, so They are removable . So, you have the engine mount bolt , onto the 2 removable right Angles,, then you bolt the RAs to the cross section. Fiddly, but, it looks like you may just have the room to get spanners to the engine to RAs, and the bolts ( I'd suggest at least 2 each mount) that affix the RAs to the cross over.
Right Angle Mounts - you can get nice, say 1'4" / 6.35mm thick 6061 Right Angle, with an inner radius, pretty easily, and, that thickness, with no weld put to it, will be Bloody Strong.
All depends on clearance(s), and thickness of the Cross section, of course.
If that was too thin, you might be able to weld 'pads' onto the cross over, for more Thread connection / interface .
I've done those sort of things, to quite few conversions / jobs, over the years.
PS : I assume that plate on the RH side of the engine is something to do with an 'Autolube' that may have been on the Blasters?
I know buggerall about Blasters. I remember when I did my trip on a DT175 pretty much around OZ, I started off with the Auto Lube removed, as that was the 'done thing' in the 70s. I put it back on, early on the trip. As, it worked, being mechanical, and, just removed the need for faffing about with extra Oil bottles, and mixing. I never had a hint of a problem with the old Yamaha Auto Lube set ups.
PS : I reckon You'll end up with Really Neat bike out of this combo!
I went with the option of welding to the crossover and making a bracket that bolts to the lower engine mount. This seemed to be the best option. Didnt go the thru bolt because of how far back the mount is. There is about .020 between the lower mount and the crossover piece.
Yes that plate is where the oil injection pump was. I bought the engine as a basket case and didnt have a good pump. If I did I may have went with injection. You are correct the yamaha oil injection is VERY reliable. The blaster engine is actually almost like the old DT200 engine. Counterbalanced 6 speed air cooled goodness.
Please keep the pictures coming - I'd like to see the solutions you've come up with.
I love seeing people have a go, and creating 'things'.
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I might need your advice on some things. Been a fun build and can't wait to ride it.
Got home from some errands this morning and these were here. Been waiting for over a week but they are unscathed.
This is awesome, keep it coming!!!
Interesting! I'll follow the process!
I've always loved an XR4 alu framed, road legal, like the BBR...
Very impressive! I've always loved the IT200's. Your rendition looks amazing! I'm curious as to what it will weigh when it's done. That blaster engine is significantly lighter than a 4 stroke not to mention there's no radiators anymore. Would be nuts if you could get it under 200lbs.
Awesome project.
Did you weigh the blaster engine? Curious how it compares to the weight of a modern YZ engine with radiators.
I will weigh it today and see. I dont tnink it will be under 200 with the stuff I have on it, I do know that the weight is lower which I would think would be a good thing. The top of the head is way lower in chassis and you lose the head/cam/valve weight up high. The carb is also lower and a lot lighter than the big FCR.
Will weigh today, the CRF engine is pretty light, but a lot of wight saved to be sure.
So about the engine....I searched long and hard for an engine and almost bought a couple whole blasters to get one. People wanted insane prices for total junk. Then rite before Christmas last year I found a complete engine with extra big bore cylinder for cheap on ebay. I put a bid in and won the auction a day later. Nobody bid on it, I think because it was almost impossible to find the listing. It didnt come up in any normal search for some reason and I found it by looking for parts for somthing else.
Notice where the intake windows on the piston face? Seller said engine ran but low on power thinks it was a carb problem. This picture was taken after much cleanup on the engine. After a soak in intake valve cleaner and gasoline (several) and several hits with degreaser it started cleaning up. It was the filthiest engine I have ever seen prob from the pipe ramming the charge back in thru the intake windows. Crankcase was full of black goo. But the bones were good, Yamaha cylinder and stock bore.
I planned to tear the engine down over the winter send the parts off and build it over the next few months. But that never happened fo a variety of reasons. Christmas day I woke up and felt like I had been run over by a train. It has been 8 or 9 years since any of us have been sick even with the wife being around it daily during the worst of the covid outbreak. I got up and got moving and felt a little better, but pretty darn rough. It ended up going thru the whole family. Multiple flu and at home covid tests negative so I dunno. My wifes good tests at work said negative for both also. Either way felt run down for about a week and didnt really feel great till after new years. Then multiple things breaking at home needing immediate attention and several problems at work that kept me there 12 to 16 hours a day 7 days a week(fortunately I do get paid for those hours)for a few weeks at a time and winter is over.
So when my wife had go to Rhode Island for work I decided to go with her and drop the engine off with Ken Oconnor. Ken is a great guy and a meticulous engine builder and he has prob ported and built more blaster engines than almost anyone. I told Ken what I was doing with the engine and what kind of power I wanted and told him do whatever upgrades and use whatever parts he would if he were building it for himself. A week later he was done and it was on its way back.
Engine has all new bearings, wossner piston, 3 mil stroker crank, hinson clutch basket, proX clutch, Rad valve, head cut for 50/50 race gas.Engine is 66.25mm bore by 60mm stroke 206.5cc. I also had him bore the cases for the CRF swingarm bolt. We decided to not lighten the flywheel or counterbalancer and Ken used a little less exhaust duration when porting it than he normally would. The engine looks great and the price was very reasonable. I am confident it will run great(if i get the pipe rite). The goal was a midrange engine with good low end and some decent top end overrev. I will be running a 28mm PWK for a carb and a procircuit pipe for a kdx200. The pipe will be another major ordeal to fit properly, but I have some ideas. I picked this pipe for various reasons and if it deosnt work well I will find someone smarter about pipes than I am to build one.
Very pleased with kens work, the engine looks great, super fast turn around and very fair pricing. He also is one of the few that does a great job eith the honda tin can cranks, so if anybody needs one done I can highly reccomend him.
To keep it real, I have had several frustrating problems while working on this project. I am not a professional fabricator or welder. I do not have a lot of the tools needed to bend and cut aluminum so I am constrained by what i can grind, wittle and cut with what I have. In a perfect world I would do things differently but default to what I can do that doesnt look horrible and also be functional and sound.
That being said I am a fairly decent aluminum welder. I wont be making videos on youtube anytime soon, but usually make fairly "professional looking" welds. If I havent welded in a while, I usually set up on the bench and weld a few practice joints to get back in the swing before the welds that count. Most times i start running a few beads start getting them looking pretty nice and consistant and dip the tungstun when i fill. Stop grind the tungstun and remember to do a slight lift when I dab the filler. I naturally hold a very tight arc and kind of lift a tiny bit when adding filler. I guess it is my style as I Know some guys do not do this and some do.
So I built this in stages and did a lot of welding on this poor frame before I cut the y out. The spars were paper thin above the pegs from years of boot rubbing and had several holes, the plastic had worn deep groves where the rad shrouds touch the frame and i had to repair several cracked mounts. All of this welding went fine and didnt matter at all what it looked like since 95 percent of it was gonna be ground down or covered. The next weekend I welded the 1 inch tube sections to make the new Y and the welding went well. I chose to grind these smooth because since i dont have the tools or skill to bend new lower rails, I wanted them to look clean. I also need every mm of space for the pipe clearance. So doesent matter what they look like as long as they are solid.
But the mounts and plate at the front I want to look decent because they are gonna be left as is. Here is where the problem starts.....
I was welding some other stuff I had to do, mainly for pratice before I made the welds that count. I was feeling good and making some very nice looking welds pretty easily. But then I started getting problems with dirty welds. I stopped and cleaned the metal, got a new gas lense and bigger cup, upped the gas a bit, played with the ac balance to add more cleaning. But none of these completely solved my issues, and I started making shittier looking welds the more I welded. It seemed like I had to weld with a bit more amps than usual, and it almost seemed like i was haveing trouble focusing the arc and putting the heat where I wanted it.
Being bullheaded, impatient and convinced I was screwing up I kept tweaking and forging ahead. No matter how much I cleaned and tweaked I just wasnt welding well. I was halfway thru my giant gas bottle, so I knew the gas was good. Here is a part I welded up on the bench, you can see the crap in this weld.
But I went ahead and made up and welded on the front mounting ears. I didnt plate them, because most of the mount is on the new 6061 tubing I welded in, which is a lot thicker than the tubing honda used. Hopefully it will be good. This is the last weld on the mounting ears. It is also the last weld that welder made before the AC board smoked....
Crf
Blaster
The crf engine is light. I did the math before and subtracting the radiators and hoses and lighter perches without the hot start all said I guestmate 10 pounds or so difference. Matbe a little more. However when you pick the engines up you can feel the CRF is top heavy and the blaster engine has all the weight at the bottom. Combined with the fact that the engine is much shorter I am positive the center of gravity will be much lower overall. I am not an expert, but feel it must be a positive for handling.
Weld Problems - sometimes you'll have them for inexplicable reasons / won't find Any reason / or, 'discover' just the one thing being 'off'.
I've TIG welded since 1974 - from using the most basic of machines, through to, at a mates place, a new model , top of the range Kempi, with all the bells and whistles. And, I don't really like it. I basically turn off near every 'feature', and get on with it.
I'm Old and Set In My Ways, I guess.
Oh, and then I get exposed to the Machinery the 2 Unis I teach 'Baby Engineers' at have. Aye Kurumba, they've got The Trickest Of 'Units', of any type available to them!
I have a (37yrd old?) Miller Syncrowave 250 in my Humble Home Workshop . I had an external Pulse Unit for it, that I barely used, and, when I decided I needed it ( my DH Bike Chainstays are made of stacks of 3 x 12.7 x 12.7 x .9mm square 4130, and 4 lengths of those ) with all of the weld bead I've created for myself, to join them, having gone from Aluminium SAs with chainstays of 38.1 x 17.45mm 6061. I found the bloody thing had carked it from just sitting there. Though, I think it burnt out, even when not in use, as charge went through the Foot Control, from it.
But, with 'The Shakes' from progressing Parkinsons, and Burnt Out Eyeballs, I'm starting to need Help, so I've bought a Jattus TIG Perfect 2.0 for it - I've had it since Xmas, but still not used it. I'm a Bloody Drongo!
A suggestion - with that V shaped divot in the RH cradle, I'd plate it. On the Inside of the tube , from the original weld point at the SA Pivot casting, a few inches past it. Wont' be seen, but will ensure, I would think, no problems in the future. You might be surprised ( well, Shocked) at how weak that section would be if you had that out, in your hands and tried to bend it
I mentioned RA 6061 with an inner radius - it's wonderful stuff for say, Engine mounts. You can weld it on as a 'Pad' weldment, much like Most OEM mounts are.
As an aside, I've also used 'T" sections, if I had a job that allowed it / I felt required weldment on 2 faces. You can do a Lot, have a lot of different approaches and solutions, with a bit of ingenuity!
While you're at it, if you intend to fit / make a bash / case guard, you might consider putting mounts on the frame for it.
I often do it with AFs I've done ( and Yes, far from 'perfect' welds) :
Sorry for putting so much in Your Build post, but, thinking about my plate suggestion at the V notch, perhaps, if you do some hard mounts for a bash / glide plate, you could do something like this, to reinforce that V area. It's a crap picture, but, you can see that the RH mount (pictured left) goes further - that was to cross over a (much smaller) divot I put into the original SA casting / Cradle tube joint to allow clearance for a CR500 case.
Though, your lower rear engine mount solution might preclude this : :
I appreciate your input, please keep up the suggestions!
I agree the bottom tubes on the frame are very wimpy. I bought 1 inch radiused 1/8 6061 tube to match the honda tube but it is much more robust. On the corners where the radius is, it is much thicker than the wall sections, very beefy tube.
I was nervous of the V notch strength and had a piece of 1/2 x 3/4 angle. I tied that into the cast piece and extended it about an inch past the notch on the inside and bottom of the tube.
When the AC board fried, they gave me no issues and actually gave me a new welder. Fortunately it was still under warrenty. I think somthing with the ac balance or frequency was going south before it gave up the ghost. The last few times I welded the tips pf the tungstun was getting these strange little balls, sometimes 4 or 5 on the tip. These were NOT like the normal ball on the tip or from contamination.
The new inverter Tigs have all these features frequencies, pulse width, wave form, pulse etc etc. 98 percent of the time i weld with 60 hz and use none of them. I just want it to work.
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I bet you're having a Much easier time now without a Weld Unit that's Fritzing out on you!
That can be a bloody NIghtmare.
It wasnt obvious at first but somthing was def up. The wierd little balls on the tungstun should have been a clue but.... It is kinda the reason I want to build this bike. Simple, not a lot of bells and whistles just what you need. Relaiable, spark and fuel it runs. l
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