fantic240motor

125 frame is the same as a 240 just has the different swingarm bearings and no need for the extra frame loop to protect the smaller 125 flywheel casing.

Interesting stuff fourex. I was recently discussing this modification with some classic trials friends and the unknown factor was how will this effect the feel of the steering especially on full lock. Will it tend to tuck under? Be interested to hear how you find it rides.

A weak point on 240 frames is the head stock braces. They will flex and crack and inevitably the steering angle will increase, not what you want at all. As most have suffered this they and need to be pulled in and the braces strengthened or replaced. Many owners decide while they're at it a steeper would be a worth while. To check yours put the bike on a stand measure from the front spindle to the swingarm pivot, it should be 890mm center to center. My 240 is 5mm over and due some work. I have measured some modified bikes and 870mm is common so subtle tweak but given the damage it's quite an improvement. I had a one once that measured about 900mm! An unmodified original 240 is perfectly usable without modification so if yours isn't damaged the choice is yours but worth while if it needs adjusting.

Can anyone please confirm this is the correct method and measurement for checking the float height on the Mikuni SE BSR33-79 carburetor. I believe you hold the carb horizontal so the floats hang, then tilt the carb just enough so the float tang just touches the float valve. The floats are then parallel to the carb base then measure between the face of the carb to the very top of the float body not the flat ledge but the highest point. Set between 12mm and 14mm. Any of this right or wrong?

This is for a 307 but as they're pretty similar to 309 might give you information you need. Fantic_307_parts_list.pdf

Don't know of lighter springs but I'm sure some there must be some the same length and diameter but with less tension out there somewhere. Just wonder if lighter springs give a nicer lever pull but slip due to being too weak, trial and error I guess. I use an extension to the clutch arm too and find the effort better but if there was any lighter springs I'd be up for trying a set.

If you think about how the forks slid up and down you can quite easily check why they are sticking. Presuming the forks are in good condition with correct oil and sound springs etc, here's a few things to try. With the bike on a stand I removed the top caps and fork springs, leaving the front wheel and mudguard brace. The forks should then slide up and down without any binding or sticking. You can try rotating the stanchions, sometimes they have a slight bend or high spot that can cause issues. Also sticking could be down to a wrong size spacer making the wheel pull in or push out the forks. Try loosing the axle or removing the wheel and see if that helps. Brake drum damage... you can get the steel lining replaced by a specialist. I have seen someone offering this service via a facebook page recently for about £45 plus postage. Alternatively find a good used one. I'm very not familiar with the rear kick 156cc engine so can't help with oil leak but hopefully the seal could be changed from outside the callings.

I've always called it a clutch cover, not sure if that the correct terminology. If you find a cover for an FM450 with a good sight glass it would save you fitting a new one to yours. Two birds, one stone! I've never seen a Fantic with matching engine a chassis numbers. I'd imagine the engines and frames were stamped separately in different parts of the factory and brought together for assembly. Frame number is on the headstock tube. As for gear oil you'll get lots of different advice and the truth is they're all probably right. ATF is favored by many as is specifically designed light gear oil. I have used both as well as 0w30 and 5w30 engine oil, all worked fine. You will need to change at regular intervals so you'll get plenty of chance to experiment for yourself.

Engine code and cc is stamped on the upper right hand side crankcase. If you have four head bolts is 212cc if you have five is 249cc.

Replacement oil level viewers are available if your's is damaged. The oil leak will be simple to fix, these bikes aren't know to have oil leak issues. Should be easy enough to see where the oil is coming from.

Yes it is threaded into the frame, sorry I said otherwise earlier I was thinking of later Fantics. Had to go and have a look at my spare 240 frame as I really couldn't remember there being a thread but there defiantly is! The other end has a 10mm allen key and the thick washer is held on by a snap ring so can be removed once the spindle is out. If your spindle doesn't have this end then it's probably from another bike. You will need to unscrew it to get it out presuming it's threaded as original or just go for cutting it as mentioned. I bought one from Bosisio Motori but they are now sold out. If Bill Pye or Bob Right don't have one then you are welcome to the one in the picture for free. It's got some wear but better than nothing until you can find a new one or possibly get a copy made, it would be a handy template.

Here's an old I have. It's not threaded into the frame just the nut on the end you've already removed. I'm guessing the ridges are stopping it from sliding back out or maybe the bearings are rusted to the spindle. I know a friend had a heck of a job getting one out of a 301.

Is the clutch slip only when you pull 5th or 6th gear? New springs are always a good idea but have a look at the plates while you have the springs out. The metal plates can wear too especially the alloy type. If I remember right the new friction plates are 3mm thick. If you've not already aware of how to clean off the glue and tidy up the friction plates have a search for "Beta clutch fix" and give the friction plates a look at. It can reduce clutch drag and slip under load. Raising the overall gearing will help your road speed but will obviously have an adverse effect on slow speed trials riding. Might be hard for a 125cc to pull the higher gearing over obstacles too. I've never rebuilt Section 40mm Marzocchi forks but I have a pair that need seals so please let us know how you get on.

Love my 250 Section but I'd not entertain a 125cc bike due to the possible lack of power to lug my 6'2" 14 stone around. Don't know if the 125cc Section suffers as bad as the 250cc bikes but as mentioned expect either damage or repairs to rear engine mount and frame down tubes.

I've personally haven't re-jetted any of my old bikes but I have found it necessary to get the octane up to avoid the unwanted knocking (especially on the over run) when hot. Air cooled bikes from that era seem to suffer from it. I use Fuelx Formula 6 octane booster with super unleaded and have found all those issues stop. Another point on all my Fantics is the pattern head gaskets I have come across are rather thin so I used two of them to bring keep the compression to the original specs.

As mentioned lots of good used upside down trials forks out there, just buy a complete set and you're sorted! I personally wouldn't pay too much attention to all the bad press USD forks get. I like the ones on my 309. For an average rider on middle route sections they work great. I saw Richard Allen (07917 406313) had a few sets a couple of weeks ago. If you go down the traditional fork route he could also help.

Wish I'd had a closer look to compare the piston on my 309 when I had it apart. Is it thought that Fantic fitted a stronger piston for the 309? Perhaps from a K-Roo?

Unfortunately my piston is way past saving I'm afraid. The picture doesn't do it justice. Those are scores, some pretty deep and the other side is worse. It'd be the shape of a 50p by the time it was cleaned up! Shame as it probably hadn't seen a lot of use before the yobs got hold of it. The lack of air filter and the amount of dirt in the air box killed it. Your tip for cleaning up a piston after a nip up is sound, I used to have that method down to a tee back in my scooter riding days!

Personally I'd do both new piston and re-plating for a proper job.

I had the cylinder re-plated along with a new piston. The cylinder walls didn't look as rough as the piston skirts. Taking the head and cylinder off isn't too technical. Nothing tricky just basic mechanical know how. If you are in any doubt about how to do it I'd get someone to help. I used http://www.langcourt.com/page27.html to re-plate my cylinder and http://www.fantictrials.co.uk/ supplied the new piston.

If your piston looks like this it's time for a new one! I doubt it will. I bought my 307 as a dead project. It had been used as a field bike and run without an air filter and not enough 2 stroke oil.

I'd say do it properly if at all. If the bike runs nice and the noise isn't too off putting then personally I'd leave it. I had my 307 cylinder re-plated and a new piston fitted as they were both very worn. It was then very quiet but now after a years use it has that familiar top end noise the same as my 309 that is original.

Smart phone videos always sound weird but all I can hear is piston slap. Not a big deal and as you have been told these Fantic's are prone to a noisy top end but still hold good compression. It's the skirt rattling so a new set of rings doesn't help. If you want to eliminate it you'll need a new piston and the cylinder re-plating that will cost about £300 all in. In case you don't know the cylinder isn't re-bored as it has a Nikasil coating that has to be professionally sorted.

Yes doesn't appear to be working. I'm sure they'll have it up and running as soon as they are back to work.

Had the same issue with steel Betors leaking a few months after buying them. I had a receipt but the supplier pointed out if I'd damaged the shaft they will leak and they were not obliged to help. I checked and the shafts did have small dinks and scratches. Betor do have a reasonably priced repair kit and I did consider ordering a set and but hardly seemed worth it since I was going to replace with the same quality so could only expect the same life span. £120 wasted! When I spoke to Falcon they said the shafts on steel Betors are too soft. After a couple of years use the shafts on my steel Falcons are still undamaged so I believe Robin was correct and not just feeding me some sales talk.