Mikkh's WPB 125 CRF 70 framed build

[my67xr]

Daytona T Rex 150 stroke is shorter than the Lifan 150 by .3mm
Daytona cylinder is shorter too by about 10mm iirc

The Lifan 150 cylinder skirt's wont fit in any of my Lifan 125 case's

Clutch basket gear's are the same

To remove some of the wobble in my rear clutch basket's Lifan, 190F, Z160HO, i use an old gearbox shim in between the kick start gear and bearing, fitting it got rid of 1.5mm - 2mm movement each way

Which grommet, the rear tank support grommet or the 2x front lower support grommet's?

 

[mikkh]

But I have the big head style primary clutched lifan 120cc 1p52 and 150 cylinder does indeed fit mine (planning to use the 52.4 cylinder and lifan 150 crank which makes it 127cc).
Well I have a 3 valve head which has 10mm shorter cylinder and has the lifan 140/150 head stud pattern and I think that should work with the daytona 150 clutch.
Planning to buy the needle bearing secondary clutched cases to try that out or port and use the 3 valved head on lifan 150 ( have extra tab welded onto it to fit any type of engine)

The nk 14/12 bearing on my lifan 150 is worn out. Hard to find a substitue for it (hk1412 is 2mm smaller outer dia). Will check one bearing supplier who has almost every bearing for jap bikes on order.

 

[mikkh]

Yes I meant the tank support grommet. Seems like jetting wasnt the culprict here, the woodruff key got sheared the second time.

 

[mikkh]

Bad updates. I will get the engine parts for christmas or if all goes well maybe few weeks earlier. Might shorten my 120cc crank right end and make the primary gear for it for use with secondary clutch.

I also thought about putting pit bike engines in 85cc jap 2 stroke bikes. But the frames seem 10cm or so short to fit the pitbike engine (cylinder head hits front wheel). Is there any way around it? Thinking of buying a blown up 85cc 2 stroke and if it doesnt work I would just make use of the suspension and sell the leftover parts.

The daytona t-rex 150 cylinder is 69mm tall. The daytona crank could make an interesting three valve engine build (the crf50 style build I am planning currently). Does anybody have info on the three valve head valve spring orientation (do the tighter wounds face keepers or valve stems?). Are there any stiffer springs available for them? The cams are same length as the e22 head ones, I will check if there are any interesting cams fitting them available.

The primary to secondary clutched engine conversion crank piece (basically a t-rex 150 primary crank gear homemade copy, planning to join the primary clutched crank gear with the cast iron primary clutch inner basket on the same principle as gearbox gears (gear dogs)) construction is going well, might finish it in the next few weeks.

Is it possible to make thread for the banjo bolt for oil cooler on those older lifan 140 right hand cases (newer ones have a banjo bolt for oil cooler on the RHS crankcase and on the clutch cover)?

 

[mikkh]

Here is the possible solution of making the primary gear conversion. I have to machine it down (use a lathe or angle grinder with somebody spinning the crank). And I need to cut the gear dogs.

 

[my67xr]

Does anybody have info on the three valve head valve spring orientation (do the tighter wounds face keepers or valve stems?). Are there any stiffer springs available for them? The cams are same length as the e22 head ones, I will check if there are any interesting cams fitting them available.

It look's like the tighter winding's on the spring's were fitted out toward's the tip of the valve, against the retainer's

Not sure about performance cam's, or spring's for them, maybe look at the Honda XR100 valve springs ?
I've never had mine apart
You could try adding a 1mm shim underneath them, but check for spring bind.

Tapping the clutch cover, the alloy isn't that thick there.
You might be able to build it up with weld and then face it back flat and drill and tap it.
Or possibly drill it out and fit a shortened Sealey thread insert like this and Loctite it into the cover

 

[mikkh]

Didn´t express myself clearly enough about the case threading.



Here is a picture that should clarify it (I mean the tab under the oil pump on right of the drain plug). The newer lifan 140s have a banjo bolt fitment there for the oil cooler. Are there any internal differences there ie some oil passages?

And this is how it looks on the newer lifan 140s (I have clutch cover of that style)

 

[mikkh]

Can crf140 14/17 wheels made to fit pitbikes easily?

 

[my67xr]

Look's like you can just drill and tap it out, M10 x1.25?

A lot of pit bike's cant fit bigger wheel's due to tyre clearance at the front of the swingarm and front tyre clearance to the head when compressing the fork's
Was there a bigwheel version of your bike available, if so you could try to find a swingarm off one, and longer fork's

 

[mikkh]

Yes there are big wheels available for my bike (it is actually a pitbike with 14/17 wheel capability). I would like to know if anybody has tried fitting them to pitbikes ie if the brakes fit, do I need crf150 front end too, does the rear line up etc.

 

[gottagetacheaperhobby]

All you can do is try, its not hard to get different sized spacers etc. I dont see the need for crf150 forks, a set of 770mm gpx black labels would be better for your purposes than the crf150f forks, and cheaper

 

[my67xr]

I'm just guessing here,
but i reckon the big wheeled pit bike's were first built using something like the CRF150 (small wheel 17/14) wheels
Then the chinese factory's found an equivalent budget version and went with that, changing spacer width's and caliper mount's to suit.
A lot of the big wheel pit bike's we have here use the same hub's as the 14/12 wheeled pit bike's.

Are you wanting to use the CRF150 wheel's because you an get them cheap or for the better quality ?
The china set's aren't that expensive around $200 AU and up.
Or you could buy the hub's, rim's and spoke/nipple's seperately and build your own set

 

[mikkh]

Thought about the CRF 150 wheels because I trust them a lot more than chinas

Where I could find that lifan 150 needle bearing? There is no standard bearing replacement for it.

 

[mikkh]

Thought about using 15mm id bearing and a bush (tightly on the countershaft). It should work I believe. I will consider looking for different countershafts.

Does complete Z160HO gearbox fit lifan 150?

CR85 has 15mm rear ale, crf150r has 17mm.
Not sure about the front axles. I believe they should work aout with zochhies.

Are those GPX black labels as good as crf150 (85 etc) forks?

I am thinking of using 285mm DNM rear shock and moving the forks up the triples, to compensate for the 1cm shorter rear shock. Without moving the forks up and using 265mm rear shock for test ride (engine is apart now, still thinking about the crankshaft options) it looked weird (swingarm almost parallel to seat ).



But 285mm rear shock should be close enough, that 295mm rear shock is hard to find (apart from generic ones).

 

[gottagetacheaperhobby]

Definitely to low in the rear with that shock, the dhz crf70 copies use te 285mm dnm so it should be perfect..
The black labels arent as good as a set of 85 forks, but the 85 forks need a lot of mods to work on a pitbike, and with good oil in them the black labels are good enough for most ppl.. I have a set of black labels and genuine zocchis, while the zochies are a little plusher I still think the blacklabels are great for the money they are worth..

 

[mikkh]

Started the primary to secodary clutch engine build. Used the lifan 150 crank and CH125 52.4 piston. The piston sits about 2mm below cylinder top on the sides. I would have tried it out today, but I got wrong rings (54mm) with the CH125 piston. Milling of the cylinder and making the cam chain shorter is a lot of work If it works without any extra work then I wouldn´t bother. The lower compression would reduce all the kickstart issues and the engine would last longer theoretically.

 

[my67xr]

The CH125 piston, did you get an oversize? standard they are 56mm, and hasn't it got a 14mm gudgeon pin ?
Lifan 150 use a 56.5mm piston and it has a 15mm pin.

 

[mikkh]

I am using the CH125 piston for the primary to secondary clutch conversion. I am using the kick in neutral lifan 120 as a base; ZONGSHEN 140 gearbox shaft to use the secondary clutch, lifan 150 crank. The CH 125 piston I used has 15mm pin and it is 52,4mm. But it sits 2mm below the cylinder top on the sides, but it is flush with the cylinder head.

 

[mikkh]

Planning to use R1 or R6 rear shock. They are 300mm and 295mm and are excellent quality. Do any other sportbike shocks fit (have vertical reservoir)?

 

[my67xr]

With the R6/R1 having linkage suspension the spring might be a bit soft, you will have to try it out.

Honda CBF110 2004 have a 295mm rear shock, not sure on the spring rating though
2004 ERA Honda CBF 1100 Showa MFA 921 GAS Filled Shock 295mm Length Silvr Spring | eBay


If you cant find anything that'd work off a Jap bike, then i'd go for something adjustable like this DNM or the Volt
DNM fully adjustable 295mm rear shock :: suspension :: Mini Bike Parts - Mini MX
295mm Volt V2 Pit Bike Adjustable Shock Absorber Suspension 140cc 160cc Pitbike | eBay
PIT BIKE VOLT RACING V2 295MM REAR SHOCK 1000LBS SPRING ADJUSTABLE COMPRESSION REBOUND

Or an Elka
Shock Elka 36PBCR Pit Bike Piranha SSR Pitster Pro | eBay