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XR145R, yet another conversion

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Well I have the bug. Time to start on my conversion.

I have a 98 cr 80 rolling chassis, My old race bike, and an 87 xr 80. My first real dirtbike.

Ill have alot of questions, mostly motor related, so I thought a thread was in order.

First a few pics, then on with the questions.

Donor frame and a randon honda 70 motor

154abmw.jpg

24mm mikuni flat slide i WAS going to use, Guess ill have to bigger

2d14ghz.jpg

donor engined bike. Might use that tank too, or make my own from aluminum.

2uf8v12.jpg

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Engine plans

Takegawa 146cc kit with +R super head and all that jazz.

^^^^^ thats more money than I have in my last 3 motorcycle builds combined.

Ti exhaust of my own flavor

lightened flywheel

oil cooler

clutch upgrade later on

flat slide carb, either 29 or 30mm, to match port size.

Here is the first question, will that top end and rotating assembly fit the 1987 cases? If not ill look for another motor.

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in the past I have shoehorned a 600 in a cr 125 frame, but that project was mothballed.

8wwrpv.jpg

was a supermoto project though

11i1jpc-1-1-1.jpg

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latest bike I built, maybe I should finish it before I start another one. 650cc single

mu7cwj.jpg

Ill mention this, right now I have 2 full frame up bike builds going on, 5 other very labor intensive builds, a drift truck build, my DD vw golf build, 2 hotrods still in the planning stages, and 2 boats im restoring. Pluss a full time job and school soon.

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Engine plans

Takegawa 146cc kit with +R super head and all that jazz.

^^^^^ thats more money than I have in my last 3 motorcycle builds combined.

Ti exhaust of my own flavor

lightened flywheel

oil cooler

clutch upgrade later on

flat slide carb, either 29 or 30mm, to match port size.

Here is the first question, will that top end and rotating assembly fit the 1987 cases? If not ill look for another motor.

yes if its a 87' 100. if you have a xr 80 bottom laying around you will also wanna rip the tranny out of that. the xr 80 has a nice close ratio rack compaired to the 100. also as you prolly already know the 87 ignition will not work. you will have to purchase either a 94 or newer oem ignition or one of the aftermarket set ups. clutch will need at least a very good set of hd springs and even at that i'm uncertain if it will slip or not highest i have went with stock basket is mid 120'scc. the stock clutch and spring setup wont even hold the additional hp of a stage 115 stage 1 kit and the stage 1 and stage 2 were gutless. that 75 motor you have crammed in there you looking to part with it?

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yes if its a 87' 100. if you have a xr 80 bottom laying around you will also wanna rip the tranny out of that. the xr 80 has a nice close ratio rack compaired to the 100. also as you prolly already know the 87 ignition will not work. you will have to purchase either a 94 or newer oem ignition or one of the aftermarket set ups. clutch will need at least a very good set of hd springs and even at that i'm uncertain if it will slip or not highest i have went with stock basket is mid 120'scc. the stock clutch and spring setup wont even hold the additional hp of a stage 115 stage 1 kit and the stage 1 and stage 2 were gutless. that 75 motor you have crammed in there you looking to part with it?

Well thats an 87, made in 86, xr 80. How different are the cases? Looks like I could pick up an xr100 bottom end from ebay for a fairly decent price. I won need the top end anyway.

The 75 motor is missing some top end parts, valve springs and keepers if I remember correctly. Would need a new piston and a bore too. Doubt it would be worth it. I just threw it in there to see how much I am going to have to cut.

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Holy Chit!!!

Cant wait to follow this thing! Keep us updated.

Very nice work man.

Diggin the bell crank on the rear of the 650. Reminds me a bit of one I did on a rod a couple years back

IMG_3181.jpg

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love that electric hotrod. Is it ever going to get a body? We have a 31' 5 window coupe we are going to build.

Settintrendz you would be the one to know this. Physically how much bigger is the takegawa +R head and jug? I dont want to rebuild this frame then have the built motor not fit.

Im also wondering if I can keep the cradle stock and re make the upper brace tube for head clearance.

I guess My first order of action should be to build the motor. Then build the frame to fit it.

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latest bike I built, maybe I should finish it before I start another one. 650cc single

mu7cwj.jpg

Ill mention this, right now I have 2 full frame up bike builds going on, 5 other very labor intensive builds, a drift truck build, my DD vw golf build, 2 hotrods still in the planning stages, and 2 boats im restoring. Pluss a full time job and school soon.

Stop everything and finish this bike.

Gotta love cafe racers.

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Stop everything and finish this bike.

Gotta love cafe racers.

Soon enough. I need to finish the swingarm. then paint and powdercoat.

Scratch that idea on keeping the cradle stock. I can keep about 70% of it though. Ill replace the 2 tubes with some .875 4130 tubing ive got.

Anyone have a demensioned drawing of the rear motor mount to the swingarm pivot? Ill make it out of aluminum.

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Well thats an 87, made in 86, xr 80. How different are the cases? Looks like I could pick up an xr100 bottom end from ebay for a fairly decent price. I won need the top end anyway.

The 75 motor is missing some top end parts, valve springs and keepers if I remember correctly. Would need a new piston and a bore too. Doubt it would be worth it. I just threw it in there to see how much I am going to have to cut.

the cases are off enough it will be more hassle than its worth. the 80 has 52mm od crank bearings so you will have will have to change bearings on your brand new takegawa crank. the 80 cylinder is about 3mm shorter than the 100 jug. that really dont concern you for what your doing but figured it may be good food for thought in case you venture on other xr builds. the biggest PITA would be oil passage. the oil passage in the case the feeds up through the cylinder into the head is offset outwards towards the clutch a good bit further than the xr 80. dont get me wrong it is possible ot make it work via milling welding a 100 cylinders oil passage to align with the 80, or drillin cases and and making a offset insert, or there is always block the oil passage off and plumb off the case by the oil pump and feed the head that way.

i have heads i need a bottom. lol thats exactly the type of motor i'm looking for something thats not worth much value to a guy cause its missing stuff or needs a bore up. cause my intentions will not be to be just leave it stock. i plan doing alot of head work and big boring it and stroking it as long as the cases and trans was good i'm in there ;-)

now to your other question. the older 1973~76 is a 4 speed and im not certain but i dont think it interchanges. the 77' and up 75 i think will interchange.

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Wow thanks for all the great info. I asked about the 80 vs 100 because I see some bore kits listed for the 80 and 100. Good to know the oil passageway is different. I do plan on running an oil cooler of some sort. When i get. Home in the morning I'll see if my 75 is a 4 or 5 speed. It shifts very smooth and easy so hopefully it will be a good candidate for a swap. Anyone ever run an adjustable cam gear to fine tune the valve timing? I wonder about that when I see people decking the heads and Changing the head height in general.

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Anyone know the exhaust port diameter of the Takegawa +R head?

Started on my rear motor mount

2e2hsnq.jpg

and figured out just how much of the cradle I have to remove

2e4ak8x.jpg

and decided im going to build an aluminum trellis subframe utilizing the stock seat with an aluminum fuel tank. Oil cooler will mount where the stock radiator mounted.

23udh87.jpg

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Well my 74 is a 4 speed. Oh well

the 73~76 xr 75's have 4 speeds. i do believe in 77' they switched over to the 5 speeds. if your 86' xr 80 has a good rack in it use that. heads up thought if you havent already read or know. these lil engines LOVE to bust kick start gears with big cc or high CR. so unless you have made yourself a set of kickstart geargs i'd reccomend turning some space maintainers and ditching the kick start gears.

yes i have slotted and degreed cam gears in the passed for a few of my lil xr's.

i think i dimensioned the +r head ill have to flip through my notes and get back to you on the exhaust.

gotta watch setting your clearance heights with that 75 motor your 100engine will be taller. hate to see you make it all pretty just to have to hack it back out ;-) looking good by the way. lookin forward to the complete project.

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the 73~76 xr 75's have 4 speeds. i do believe in 77' they switched over to the 5 speeds. if your 86' xr 80 has a good rack in it use that. heads up thought if you havent already read or know. these lil engines LOVE to bust kick start gears with big cc or high CR. so unless you have made yourself a set of kickstart geargs i'd reccomend turning some space maintainers and ditching the kick start gears.

yes i have slotted and degreed cam gears in the passed for a few of my lil xr's.

i think i dimensioned the +r head ill have to flip through my notes and get back to you on the exhaust.

gotta watch setting your clearance heights with that 75 motor your 100engine will be taller. hate to see you make it all pretty just to have to hack it back out ;-) looking good by the way. lookin forward to the complete project.

Thank you. I have alot of Ti to build an exhaust out of, but Im pretty sure its all going to be too large of a diameter.

Im only re building the cradle with the 75 motor. once I have the 100 ill make the mounts and set the top tube height.

I might make a special valve cover so I can adjust the valves with out pulling the motor.

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so I got distracted and started working on this bike again.

s49zyr.jpg

What you got going on there???

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