Just an update to this project.
I installed a new coil (they took ages to arrive into the country hence the delay) and the machine now starts and runs really well.
I took the advice and changed the main bearings. TO be honest, they probably didn’t need doing, but once it was all apart it seemed silly not to.
So apart from a coat of paint (unlikely) and a small oil leak from the rear gearbox, all systems go.
Thanks for all the advice and for the great resource.
Cheers,
Jim
Excellent, thank you. I have now found the source of the problem, the drive gear for low speed has about 20% of the length of the teeth worn away, I’m guessing from being forced into gear with the clutch engaged or from the belt dragging. I plan to repair it by rebuilding with Armoid welding rods then grinding/filing back to get the tooth profile.
The problem I now have is how to get the drive gears off the little shaft that comes from the worm drive. I have removed the castellated nut but I can’t work out how the gear is on the shaft, it looks to thin to be splined and it ain’t shifting with a puller either.
Copy of gearbox page from parts list in photo below and attached as pdf so you can download it.
Attachments:
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Yes, all fluids were topped up before it was used.
Was there correct amount of oil in gearbox?
Hi,
I have a Howard Bantam rotavator, re-engined with a Honda. All was well until yesterday, it now won’t stay in slow gear and fast gear won’t engage at all. I am struggling with getting it apart to find the problem. I have removed the rotor assembly, “opened” up the LHS frame and removed the axle, and that is where I am stuck. The wheel assembly moves about 40mm away from the gbox but won’t come any further.
Can anyone help me with removing the wheel assembly and further stripping, and also with the likely cause/repair required.
Thank you
Hi chaps.
Well I am mostly there anyhow.
Thus far I have new rings, points and condenser. I’d have changed the coil too probably but there don’t seem to be any in the country from the usual suppliers.
I won’t bother with anything else until I change the coil now, but if I have time I will split the case and check the main bearings. I do know that the small end is OK.
Thanks for all the advice. I really like the challenge, and do want to achieve an engine that starts first pull to.
Ta, Jim
Andy, I agree wholeheartedly with your comments about the ignition system. The coil on the Mk25 4 stroke on my Trusty Earthquake gave up the ghost so I renewed coil, points and condenser, it starts first time every time, £75 well spent.
Jim , I fear you may be looking at problems that may well not exist. My first action on any Villiers twostroke , is a complete stripdown , firstly, and in my opinion , get the ignition unit tested on a proper purpose built tester , if the coil shows ANY sign of weakness , renew it , the condenser will either be OK or Duff….no half measures.
Next step(assuming the big and little ends are OK) is to asses wear on the main bearings and seals , yours will more than likely have the far better brass gland bushes for seals (later 25Cs had conventional oil seals) , if either the bearings and seals show any signs of wear , again renew them.
Lastly check the cylinder for wear , more often than not a new set of rings will cure the problem.
I’m fully aware this may sound expensive , but trust me in the long run it is money well spent , it will put the machine back into service for many years to come , and will give effortless starting.
I have a 25c on an Auto Culto , that I gave the full works to , admittedly I had all the parts already on the shelf , but it is now a joy to go to it , and see and hear it start first pull every time.
Andy.
If the carb does not flood then i can see no reason to fit a new fuel inlet needle.I dont remember reading or seeing any reference to the float height.
Hi guys. Thanks very much for that info.
Andy, I get a nice strong spark, so I think that the coil is OK. I am loathe to spend another £60 on a coil if I don’t need it. I think that the timing is still a bit out so will adjust tomorrow.
Stuart, great info about the needle – I knew it was the mixture but could not find any info about adjustment.
I never split the crank case, so don’t really know about the crank bearings at the moment. There is a bit of vibration, so wouldn’t be at all surprised if they were worn. I’ll change them if I get further on with the machine. At least when it does run all the gearboxes seems to be working ok and I have both drive speeds and the tines working.
One last thing, I suspect that the brass arm that sits on the float and lifts the main inlet needle may be bent. Is there a measurement for setting the float lift? Is it worth renewing the needle and seating?
Thanks again.
Jim
Remove the crankcase drain screw at the bottom of one of the alloy crankcase halves.This will drain any fuel residue laying at the bottom of the crankcase which will (or should !!) make starting better.When doing this do NOT pull the engine over with the starting rope in an attempt to speed the draining process as it may start and run out of control (due to over lean mixture / air entering engine where it should not).
The Villiers “Lightweight” carburettor has a small brass screw in the center of the throttle slide.Screwing it in weakens the mixture as it lowers the tapered needle and visa versa.Adjust this brass screw so that the tapered needle measures 2 and 3 eighths of an inch from the bottom of the slide.Just one more thing……make sure the engines main bearings (MS8 type) are in excellent order because if they are worn the flywheel WILL come loose and ignition timing will go out due to excess vibration.I have worked on many of these engines and you soon get to know when you are working on a good one !!!.Hope this helps.
First things first , MAKE SURE your ignition system is all A1 , it sounds to me as if that may be your problem.
Andy.
Bugger – changed the mixture to a more sensible ratio and now I can start it again.
Turns over with a drill and I just get the occasional fire.
Anyone have any experience setting up the V648C carbs?
ta, Jim
Well after a bit more tinkering, she’s running.
Lots of miss-firing at the moment as I have an oily mix to bed the new rings in, but I have throttle control, and drive to both the wheels and the tines.
Hooray!
Not managed to start when hot yet – I guess that’s a 2-stroke thing. Any tips?
Also, what oil should be in the bottom of the air filter cup?
Actually, I’ve not got a hose on at the moment which probably isn’t helping the mixture either.
Jim
