ken_hosking

I aim having difficulty with the wiring of a lanyard kill switch for a 74 Sherpa T 250. The bike has previously had a multipurpose switch but this has disintegrated. I have eliminated the leads to the lights leaving three leads. I still have a spark with any combination of these leads. Any advice would be much appreciated.

There are more riders in the Beta Factory team than just Bincaz and Grattarola. I believe that the photograph is that of Carlo Alberto Rabino, who is not a Factory rider as I mistakenly suggested. However, Beta lists Lorenzo Gandola, Sondre Haga and Aniol Gelabert as Factory team riders in Trial 2. The photograph was taken during an arena style trial and that might explain the reason for having a larger fluid reservoir.

In the attached photograph of a Beta, being ridden by a works rider, there is an interesting object in the intake area. Could it be a fuel injection system?

Yes, that is indeed the probable explanation. I had overlooked the fact that the hub and pressure plates can move independently from the basket, albeit by only a small amount. Thanks for that insight, bikerpet.

My view is that when the clutch is engaged the clutch plates can't readily move in the basket as the whole assembly is locked up. My best guess remains that the noise is caused by backlash in the primary drive gears, or the gearbox, caused by the pulses coming from the engine, as you noted. I should perhaps have started this post as an all-bikes post, rather than a Beta post, as they all do it, as technowaldo rightly pointed out.

My purpose in raising this matter was not that I am at all worried about the noise, but rather that I would like to understand the mechanism giving rise to the noise. Who knows what insights might be forthcoming from the discussion?

Thanks for the feedback Dan: I felt certain that you would have a theory relating to the noise. However, I continue to be of the view that it is gear backlash that is causing the noise. The primary drive and gearbox gears are straight cut rather than being helical in all trials bikes (to the best of my knowledge) and gear chatter is to be expected when the gear train is not loaded. Just to add another variable to the mix, some trials bikes make more of a whining noise than others. Presumably this is a machining tolerance issue in the components of the drive train.

I am interested in opinions regarding the so-called clutch rattle that occurs when the engine is running, but which lessens when the clutch lever is pulled in. My view is that the noise does not come from the clutch at all, despite the commonly used name, because the noise is at its loudest when the clutch is engaged and the clutch plates are locked together. I suspect that the noise comes either from chatter in the primary drive gears or chatter in the gearbox; probably the latter as the gears in the gearbox should be stationary when the clutch lever is pulled in. It’s not just a Beta issue, as all the various brands that I have ridden have made the same noise.

Colour scheme seems to be imitating that of the Vertigo

If the noise diminishes when you pull in the clutch lever, it is indeed something that all trials bikes do to a greater or lesser extent. Whilst the noise is often referred to as clutch noise, I believe that it is caused by backlash in the primary gear train, because when the clutch lever is let out, the clutch is locked up and is unlikely to be making any noise itself. I suggest that, if the primary gear train used helical rather than straight cut gears, the noise would be much less intense.

I installed new main bearings in a 2011 Evo 290, reassembled the bottom end of the engine and, before proceeding further, checked that gear selection was working. With the engine in the frame and the chain on, I was able to spin the gears and check gear engagement. However, I could only select first, neutral, second and third before the selector drum appears to jam. I pulled the engine down again and checked the assembly instructions in the workshop manual, but on reassembly experienced the same problem. On my 2016 Evo I can select all the gears when the engine is not running merely by moving the bike back and forwards to enable the selectors to move. Anybody have any ideas as to what I might have done wrongly in reassembling the gearbox on the 2011 bike?

Hi Booty, the bruvs went to the WTC round in Corsica in 2014 and pre-purchased tickets via a web site that the organisers had set up. A search of the web might be worthwhile. The same system operated for the two WTC rounds at Maldon in 2012 and 2014. We also visited the Beta factory in Italy and I am certain that a tour could be arranged there if you promised to sell the old 4RT and to move up to a superb Italian trials bike! Regards Ken

1.5%, ie 15 ml/litre equates to a fuel to oil ratio of 67%. In company with other Beta riders in our local group, I use an 80:1 mix, that is, 1.25%, in my 300 Factory. The bike seems to run more cleanly on this ratio than on the recommended 1.5%. Using a 98 octane fuel for this model seems to be mandatory unless you enjoy hearing detonation from the engine. Riders of Gas Gas and Sherco bikes often mix their oil and fuel at 1.0% (100:1) with no apparent detrimental effects. I suspect that the Beta recommendation of 1.5% is highly conservative for off-road trials use, but for extended on-road usage it might be prudent to increase the oil/fuel ratio to the manufacturer's recommendations.

Not sure if the video about which you are complaining is the FIM official summary or something else as we don't have Motors TV down under. However, I have long been a critic of the FIM summary videos that waste half of the film time on 'atmosphere', cut the individual scenes right in the middle of manoeuvres, are massively overproduced and which have truly horrible music that drowns out the sounds of the event.

Cascao is correct. Removing material by stamping is a far easier and cheaper process than machining a recess, with tolerances that are suitable for anodising.