j125 / tzr 150/ reed valve

i am on with my j125/tzr/reed valve conversion, this is where i am upto...

crank, split and awaiting final choise of rod. it will be this week i hope. possibilities include yam rs 125,
yam dt200, yam rd250/350. each of these have fitment issues but i want a long rod, 105mm would be good. reason, when using a reed block it will give more clearance over the case and cables.when using a packer of around 12mm . 2 mm is need if using the tzr piston and standard rod (95mm centres).

piston is a yam tzr150 with one window welded up. 21mm little end this also has an influence on the rod selection ( ready to fit).

head, standard reprofiled to suit piston ect.

carb, 24mm oko flatslide powerjet . small, cheep and available with or without powerjet and will fit to the reed block perfectly

reed block, lth early version. again very compact and used with a v forcce reed block. also this early version has slotted stud spacing ( currently in negotiation for a second hand but never used) .

pm tuning boost bottle, why not (ready to go on).

ignition, 12v electronic. af converted flywheel, px coils onto vega back plate. chiselspeed adjustable timing retarder gadget. ducati cdi and varitronic regulator. mounted under the tank. frame cut and a small compartment with a lid to house the reg and cdi (all parts are ready to go on).

exhaust. new old stock allspeed ( will have in the next week or two).

cylinder. j125.not yet tuned but rebored and honed to suit the tzr piston. i will be asking mick abbey to do the job.

the frame will be cut to clear the cylinder, but i will use a j125 starstream engine to see if it clears the frame as the rear shock mounting is different to a vega and used with a series 3 shocker.

j range hubs and rims front and rear and dampers on the front.

thats it for now. cheers simon

Simon, sounds good all that. Mick Abbey is the man for tuning he's done my J125 barrel work with good results, just short of 60mph with a gps. I have started collecting the parts for a reed block conv and already spoken to Mick about it. My reed block is a bit on the big side and i would prefer the smaller LTH version perhaps i'll have a re-think on that.
What are you expecting speed wise? When i had mine on the dyno it came out just under 9bhp will the reed give more grunt or just better fuel consumption?
Keep the good news comming

i am after a reliable top end of 60mph anymore will be a bonus , i think with the reed valve i should get a bit more low end grunt, . i am not bothered by fuel consumption, with the real quest being for reliability. the crank may have to be machined down on the webs to accept the new rod this in turn will lighten the crank . also the flywheel will be lightend aswell. we will have to have a dyno shootout

Very interesting post. Just what we need on here. How about some pictures?


Thackers, how do you find the vibration on yours since you had it tuned? Are either of you concerned about this following your reed black conversions? Just wondering as I have heard that excessive tuning does cause a lot of this.

At present without the reed vibration isn't too bad, There is some especially when revving out in 3rd but after that is feels ok. The other day when out with the gps there was a ticking which i thought was the speedo or or it's cable. It turned out to be a broken headlight bulb i've put some sponge chushioning in there now i'm sh1t scared i'll break the headlight lens. The headlight positioning is something i haven't quite mastered yet. I have fixed mine with the two main screws either side of the lamp and cut some rubber tubing to sit behind the light lugs with the other end cut at 45 degrees which then rests on the headset base where the screws fit. There must be a better way or is there an adjuster i dont know about

some pictures of the electronic mountings and the small compartment would be nice, not got my frame into paint yet, so its still possible to chop and change thigs around somewhat.

Simon, where did you get your TZR 150 piston please

Snails wrote:Very interesting post. Just what we need on here. How about some pictures?


Thackers, how do you find the vibration on yours since you had it tuned? Are either of you concerned about this following your reed black conversions? Just wondering as I have heard that excessive tuning does cause a lot of this.

i will take some pics over the weekend if i get chance as for the vibration i have orded some new mounts from rs components and the long rod may reduce this minor issue

Thackers wrote:Simon, where did you get your TZR 150 piston please

i got 2 via ebay 1 was a patern part (makita or something) the other is a genuine yam there is one on ebay now. the yam one was about £20 . just to note the little end bearing on the tzr is 21mmx19mm, j125 is 20mmx20mm

here is a pic of my crank in bits, you may have seen this on another forum



the odd shaped peg is a drift we turned down to push the crank pin out , i think you can just see on the pic where it was starting to mushroom over. we must have had over ten ton on it before it started to shift

littlemoon wrote:

Thackers wrote:Simon, where did you get your TZR 150 piston please

i got 2 via ebay 1 was a patern part (makita or something) the other is a genuine yam there is one on ebay now. the yam one was about £20 . just to note the little end bearing on the tzr is 21mmx18mm, j125 is 20mmx20mm

All i can find are TZR 125cc and 250cc, Have you got a link??

here is a link for the bushes i will be using

http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=3011441

again slight mods are needed to fit

here are some pics of my frame





















just some small brackets to fab up to mounte the cdi and regulator to . oh and i might have me rod on friday

here you go thackers

TZR EBAY 150

Although I think the listing suggests that you can use this with the std J crank without worrying about the pin sizes???

What CC does this give in the end?

Thanks for the link, i'm really wanting to get a piston from elsewhere as i have had problems along that route. Where does he get them from?
It all works out cc wise around 135cc, that's with a Jap conrod and the TZR 59MM piston, i think the Kawasaki version is near to 140cc but getting hold of the pistons is hard and expensive

very good that simon, certainy better than what i was planing, where will you route the stator wires from though? inside the frame along with the loom? possibly a neater way

yep just as you said unless i think of anything else

con rod should be here tomorow

i got a new rod today, yamaha rd125 was the winner . j125 is 95mm centres, yam rd is 110mm centres little end is 21x18. crank pin is 22mm, j125 is 18mm so will have to machine this down also big end width is 16mm and the j125 is 12mm so 2mm off either side of the webs. so this is the next job plus a 17mm packer

tomorow i will be making a dummy crank pin out of ally so that i can try the crank in the casing and cylinder. i hope it fits, its 15mm longer than standard

dummy pin on the way for trial fitment of the crank and the 22mm rd pin is getting ground down to 18mm on the ends (stepped). next it will be the crank webbs getting some attention, 2mm off the sides.

here is the start of the packer plate, a nice thick slab of 150mm billet ally. just under 20mm thick at the moment. it will be lathed down to 16mm thick with a 65mm hole. two gaskets will bing it back to the required 17mm. i will also be adding a 2mm thick cooling fin when machining down the packer





oh and a shot of my bush, ooh er missus

i dont like that, it would look far better trimmed down
have you got the old mounts out? never seen the correct tool in real life but i do have a diagram somehere

gurning beer and brute force + hacksaw. the main bolt was siezed on one mount and the fact i love the smell of burning rubber forced me into this option

we will now be having 3 cooling fins as we now have a good parting tool for the lathe . as progress is moving on a record pace i am now thinking of fuel flow or the lack of it, i am thinking along th lines of a diaphram type fuel pump driven from crankcase pressure, a hole in the new packer could be the ideal place ?. https://www.youtube.com/watch?v=7GL6LH6ufhM

i have had a total re think on the ignition. it will be a varitronic, the flywheel boss has already been swapped for a j boss. i need to machine down the back plate on the stator and thats it , power feed for water pump