I had a similar problem on my Beta TR34. The rebound on early forks isn't great. I tried various things but in the end settled on heavier oil and it stopped the top out.
I have a Campionato and recently had ( or so i thought) an issue with the ignition. I obtained another stator fitted it and kicked it over with the plug resting on the head to check the spark. There was no visible spark even though i was in the garage where the lighting is not brilliant. Felling rather fed up i checked the connections and wiring etc but found nothing. I eventually put the plug back in and tried it. It started and has continued to do so.
Beta used the same VM26-208 carb up to 2007 with a brief experiment in '95 using the DelOrto. Any dealer should be able to hook you up with a new one but they are not cheap. Stock jets on the later bikes were 30 pilot and I believe a 145 main. Your needle/jet slide may be different too if this was pulled off some other bike and "retuned" for the Beta.
Hi Dan
Thanks for the info on the jets, I'm going to order some today:-)
i have found that sizes can be different in between different manufacturers when the number is the same ,but someone could of filled them bigger ,, it could be running rich at low revs blackening the plug and lean top end causing the bogging down unless fuel level is low in bowl , i would start with some new jets in the mikuni of correct size maybe see what sizes are used on later bikes with mikuni like a zero or techno , a faulty stator could give similar problems ie if low speed coil ok and hi speed coil is faulty this would also cause black plug as fuel will not burn correctly ,,does it rev up ok stationary ? does the choke make any difference
Thanks for the reply. Your comment about the ignition has been in the back of my mind too. The bike has the original Motoplat system fitted and I have read that its a good idea to change it to the later Ducati ignition. The bike does seem to rev out while stationary albeit a bit slowly and with a little smoke but only what i would expect from a bike of this age. The choke doesn't seem to make to make a great deal of difference when operated while running. I think I will get the correct jets and go from there.
I have recently purchased a 1989 Tr34 Campionato. The carb has been changed from the original dellorto PHBH26TD to a Mikuni VM26 (I'm unsure if it genuine or a copy). The bike runs ok at low speeds through sections but when the throttle is opened up for a climb or the tackle a larger obstacle it seems to bog down. Checked the plug and it is black and sooty.I have stripped the Mikuni and checked it over, the plan was to put a rebuild kit in it but soon found that the pilot and main jets have been messed with. For example the main jet said it was a #87.5 but it was way bigger than that. like wise the pilot has been increased in size over the stated #20. This was done by comparing with new jets I had.
I believe in or around 1990/91 Beta fitted a Mikuni VM26-208 carb to the bikes instead of the Dellorto so i would like to know if the VM26-208 carb is available (I can only find a VM26-606)and what is the difference between the 606 and the 208? Or would I be better off getting a new Dellorto PHBH 26SD as an alternative?
Hi I have a 2nd hand Dellorto you can try if you wish if your over this way.
Hi Mike
Thanks for the offer. I have ordered a recon kit and some jets for the Mikuni so I will try to get it running right with this carb. Once (if) I can get it running better at the top end I will then consider what to do from there.
I presume the original is a Dellorto PHBH 26mm. You can still find them on ebay, This carb was also fitted to the early Technos but later superseded by the Mikuni. I have a Mikuni here from a 99 techno. Inbox me if interested.
Hi rgvlc
thanks for the info. The bike has a Mikuni on it now but I as I am unsure of its history (I have recently bought the bike). It isn't running properly and the carb looks very old so I'm just deciding whether to replace it with another Mikuni or go back to the original Dellorto.I don't suppose you know what setup (jets, neddle etc) was used as standard on the Mikuni's do you?
I have a 1989 TR34C. Parts for these bikes are difficult to find especially the rear guard. So I thought maybe someone may have had some experience with sourcing and fitted an alternative rear guard maybe a Gara or Techno for example? I know its a bit of a long shot but I'm you never know:-)
Has anyone had experience with replacing the front fork bushes on a TLR 200 (35mm forks)? I have a set stripped down for an overhaul and noticed that the bushes are showing signs of wear. How easily should they come out?
Interestingly, there is no part number showing in the parts manual for the bushes! Maybe they are not supposed to be replaced?
I have a 250 mono in bits at the moment so easy to measure and copy.
Can I ask why you want to build one as I bought this one to use as a twinshock!
Hi 4stroke
It's a good question. Here in NZ, trials isn't as popular as in the UK so the restrictions on bikes is not so severe. As long as you have an aircooled bike you can ride. We have late aircooled GasGasers through to TL's and even some old british bikes competing against each other.
The other reason for wanting to do this is that bike building is fun
Regarding your offer of measurements etc, yes please especially the front mount for the shock. Also some good photos be be really appreciated.
I'll pm you a drawing if you don't mind and perhaps you could fill in the measurements for me?
and there is a unused modified mono s/arm listed on ebay from time to time,
( Ian at J A M Sport , I think )
I have the tank cover mould ,which is different to the twinshock one, as there is no flared parts for the shocks mounts.
Hi motomike
thanks for the email. When you say you have the tank cover mould do you mean its the mould that was used to make the cover or you have a tank cover ready to be fitted to a bike? I hope that makes sense
Fantic 200 Forks Topping Out
in Fantic
Posted
I had a similar problem on my Beta TR34. The rebound on early forks isn't great. I tried various things but in the end settled on heavier oil and it stopped the top out.