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Discussion Starter · #1 ·
So my CRF50 has a TB88 stock head kit on it currently. Well I want to upgrade to a race head but I can't afford it so I'm looking at changing out the piston to the Takegawa R-stage piston, and throwing an E22 head on it. I'm pretty sure that the older C70 heads will work with this piston, and the E22 heads say they fit the old C70 so this looks like it could be an ideal (i.e. cheap) way to make reliable power... I've been reading a lot, but until the parts get here I'm still not sure if it'll work. Is Terry from Firepower still active on these forums? Thanks for any input!
 

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Discussion Starter · #2 ·
Still waiting for these parts to arrive in the mail but rumor has it that the R-stage piston will in fact work with a large dome 70 head on a crf50 crank...can anyone confirm this?
 

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Discussion Starter · #3 ·
What about this, can someone explain takegawa to me? Like whats the "R" "+R" and "+D" actually stand for? Also does anyone have any photos of a Takegawa R-stage installed at TDC without the head? I seriously doubt it but just trying to find ANY information I can use since all the real motor head builders obviously aren't around anymore... Does anyone possibly have any photos maybe comparing the kitaco ultra,dr atv ultra, crf70 or takegawa R stage or regular head? just grasping at straws!
 

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Discussion Starter · #4 ·
Well my parts showed up today! The head is a typical chinese head, I got the cheapest one I could find after finding the Takegawa piston kit BNIB for 40$ on ebay. Upon closer inspection its got the same dimensions as this piston but the takegawa unit has a much finer finish : 52MM_PISTON_KIT MUST_HAVE_BIG DOME_HEADS!! XR50/70 CRF50/70 (Z50R_82_TO_99) W/BIG_DOME_HEADS (LONG_RODS) BIG_DOME (OLD_70_DOME) (1004K) SO things are looking good. I've already got the head torn down for some port work and its actually not as bad as I would expect for a 35$ complete head so hopefully it all plays nice together but if it doesn't I can always pop for a TB race head piston. One thing I noticed is that it has an anti-kickback mech, and dual valve springs. But taking out the valves/springs I found the springs were sitting on bare aluminum in the head. I know honda uses a steel shim for the springs to sit on so I'll have to see if the stock honda ones fit when I re-assemble the head. Anyway, this is what I'm working with: Takegawa R stage piston, on a stock crank (long rod?), in a TB 52mm cylinder (stock head kit cyl. so I think its considered short?), all topped off with a generic chinese head until I can find something better. Does ANYONE have any kind of input or advice for this set-up?
 

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Discussion Starter · #6 ·
Yes I was planning on claying the head but I don't actually know what to do with the information that it would gain me right now...actually at the moment I'm just hoping it goes together without piston interference with the head! So update time! Got my stock head off the bike and now I have both heads tore all the way down. I'm gonna tidy up the new head a bit. The ports are huge compared to the stock head! So I think I'm just gonna smooth them out a bit, and then cherry pick anything I can off the oem honda head (the oem steel washers under the valve springs fit perfect, the stock bolts are better quality, and any OEM covers I can re-use) Then before assembly I was gonna lap the valves. Getting ready to install the piston now so wish me luck!
 

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Discussion Starter · #7 ·
Ok, so like I was expecting there was a tiny bit of piston contact with the head so I adjusted the head a bit by grinding down the spots it was hitting until I could install the bare head on the engine without a head gasket and turn over without contact. I figure once I put my head gasket in it'll have plenty of room. Got all the rough casting cleaned up and its almost ready for re-assembly. Hopefully the valves don't hit now!
 

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Discussion Starter · #8 ·
Well I got everything installed and put together and she wouldn't start. After a few minutes of head scratching I pulled the plug and whattaya know the piston was brushing the spark plug just enough to fold the electrode shut. So I tore everything back down, opened the spark plug pocket on the piston (even though I really didn't want to modify this piston, it was my only choice) and got er all buttoned up. She fired first kick! Runs great even with my crappy little 19mm carb and let me tell ya, its a whole new beast now! Pulls much harder mid to top end of the rev range and really winds out nice! 2 gear actually feels like 3rd gear used to speed wise! SO for anyone looking for a fun project, this frankenstien miss mash of parts WORKS! Cant wait till I can really tune it, and upgrade the carb. What size carb would you "guy" recommend? Maybe 22mm?
 

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Discussion Starter · #9 ·
*crickets* Well for anyone who cares I decided to port match my intake manifold to the new head and the bike wants to stall a bit at idle (unless I feather the throttle) so I'm guessing I need a bigger jet for the pilot. She's got a lot more useable power now though. Anyway heres a pic of the bike before the motor work...Need to snap a few new ones now!
Land vehicle Vehicle Supermoto Motor vehicle Motorcycle
 

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Discussion Starter · #11 ·
Thats a huge complement coming from T Bolt! Turns out a new plug solved all my running issues! I may end up keeping this cheap *********** 19mm carb as long as it holds the wonderful tune it currently running. I wish I would have taken pics along the way but next time I pull the head I'll for sure get some decent snap shots. I spent too much time in that sucker not to get a few I forgot to tighten the stupid cam chain wheel that sits inside the cylinder the last time I had the head off and first kick I heard a it hit the floor. DUH! Good thing I forgot to turn my key on, but why wouldn't honda use a left hand bolt on that bugger!? So I ended up having to pull the head TWICE which was a bummer. Anyway, time to go through all the street legal red tape...
 

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Discussion Starter · #12 ·
I know this thred hasn't seen much action, but I'm thinking about throwing a 4 speed in this bike before summer. This got me thinking.... "while I'm in there" what about a stroker!? I'd hate to tear this b!tch down for the transmission and regret not throwing a crank in since I'll already be "ankles deep". What would you guys recommend to take it up a notch in the torque dept. so I can gear this thang a bit taller? Is it a 51mm crank I'm after? What else would I need to change on my current set-up? Longer cylinder? Head studs? cam chain? etc? I haven't done much research on this subject but I only wanna split these cases once!
 

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A 4 speed trans and stroker is a good choice. You'll definitely see a torque improvement. I have this setup with a pretty small rear sprocket and the bike is still torquey as hell, but still very fast on the top end.
 

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For the trailbikes 51mm crank you keep your existing cylinder and studs/cam chain.
If you only want to split them once, you may want to bore the cases for a 54mm cylinder while you have the guts out.
 

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Discussion Starter · #15 ·
Good idea joel, I'm a tinker'er so I may actually do that purely for future upgrades. I really like how its running and driving now, so I'm still on the fence about stroking it. Would I just need the 51mm crank then? Wouldn't I need to change the piston? Ideally I would like to only open the cases once so I don't wanna miss my opportunity to increase my displacement. BUT I also don't wanna loose reliability or open up a can of worms needing to change a whole bunch of stuff to make it work. So from others with this set-up, is it worth it? or should I just do the 4 speed and enjoy my frankenstein creation motor and worry about more displacement down the road? This is a street/stunt bike, but I'd love one more gear for higher top speed on longer distance drives. I'm actually getting ready to do a GPS speed run now...
 

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Discussion Starter · #16 ·
Drumroll please............My top speed for today going down a very slight hill is........ 38 mph. C'mon bro thats it!? I thought a stock crf50 could hit 35 on flat?

However it does hit 38 rather quickly and I'm able to do 3rd gear sit-downs with a light pull on the bars now which is wonderful. So I've got a 15t front sprocket coming, (stock 14/37 currently) hopefully it doesn't take away too much bottom end but if it does I can always fine tune it with a new rear sprocket too. I'm gonna see how 15-37 feels and go from there.

I'd like to comfortably cruise at 35 without the bike being revvvvved to the moon but thats looking like more then a sprocket change! I know the AHP transmission is a decent value but are there any other transmissions I should consider using? There are a lot of options on the honda50 gear ratio calculator (but the AHP isn't listed!)

What I want is 1st through 3rd close to stock (maybe spaced more evenly) and a really high 4th gear. Like an overdrive gear just for cruising on the street without revving its tits off. Anyway I had fun today and the bikes runnin' good so Im happy!
 

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Discussion Starter · #17 ·
LOVIN THIS WEATHER! Was up in the 70's today! So I got a 16t sprocket locally and threw it on and its perfect! I got up to 43mph! And I can still pull off 3rd gear sit downs pretty easy so I'm happy with that on the stock trans! Not that anyone really cares here lol.
 

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LOVIN THIS WEATHER! Was up in the 70's today! So I got a 16t sprocket locally and threw it on and its perfect! I got up to 43mph! And I can still pull off 3rd gear sit downs pretty easy so I'm happy with that on the stock trans! Not that anyone really cares here lol.
what are you running in the rear sprocket??. I'm running 15/37 on my fresh tb88 RH build and still feel like I need more speed.
 
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