nzpeterb

Although this post is old, I am replacing the swingarm bearings and pivot on a 2014 GasGas TXT250 and have both the All Balls kit and new GasGas parts on hand. I have not tried fitting the All Balls kit but did measure the difference in swingarm pivot length when used with the same brand plastic spacer. The All Balls swingarm axle is 0.3 mm longer. I have no idea if this length is enough to be an issue, but would be surprised if the tolerance was this tight. If when I use the kit in future is won't tighten I will machine the extra length off the pivot shaft. Regards, Peter.

Now I see this question has been asked before. Front brake arm - SWM - Trials Central From this past forum discussion I see b40rt enjoys sparring and keeping the argument going, then resorts to being personal/rude. With no other useful contributions evident I will save everyones time and end my involvement in this topic, letting b40rt jump straight to being rude!

b40rt, Not sure what debate you want. My question was a request to be enlightened on the advantages (if any) of changing the front brake lever from rear facing to front facing. Your response suggested it worked better on SWM as it improved the cable run. I don't think this is relevant for the Fantic 200 as the cable run is already good. The other response talked about the effect of actuating the brake based on the direction of wheel rotation. The brakes are conventional drum with one leading and one trailing shoe, so the wheel rotation will not have any impact. By comparison a twin leading shoe brake is designed only for the wheel rotating in one direction, but this is not what the Fantic has. The only advantage I have identified to moving the arm to face forward is to overcome a worn brake cam. Changing the direction of cam rotation will use a different face on the cam. If the drum is true and the linings are good (soft for trials) then the next steps to improve brakes are a longer brake arm, or changing handlebars levers to ones with a different fulcrum distance. Regards, Peter.

Grib are selling kits to move the front brake arm from facing rear to facing forward on the Grimeca brake as used on the Fantic 200. Has anyone done this? If they use the same brake cam, and the arm is the same length, what is the advantage of rotating the cam anti clockwise instead of clockwise? Regards, Peter.

Section Swept. Thanks for the additional reply. I was able to try another Dellorto PBHL25BS carburettor today and this resolved the current issues and confirms the need for a replacement carburettor. As it seems no-one has experimented with different carb sizes, and I don't want to pay for a carb that doesn't work well, I have decided to purchase the original size. I like your suggestion of trying different diameter collars though so will look at how to achieve this. You are right that the Fantic offers no scope for extending the inlet tract unless a custom air box is used. Your mention of the IT range reminds me of the boost bottle I made before these were in vogue. A 75 mm irrigation tube the size of a baked bean tin connected via a hose between the carb and reeds. Not sure it increased response but the bike idled much better and would idle as long as you kept fuel in the tank. I think its best use was psyching out other competitors on the start line rather than any increase in performance. Thanks again for taking the time to reply. Dellorto (Eurocarb) have also been good, so I have learnt a bit by asking these questions. Regards, Peter. PS All my riding is low altitude so this one variable I can ignore.

In case anyone is following this I am adding a note to complete my reply above. I have been talking to Dellorto and they confirm the venturi pressure is related to slide diameter not carburettor bore diameter. The 22, 24, and 25 Dellortos all use the same slide diameter so I now understand Section Swept's original comment that they will all have the same venturi pressure. I guess this also explains why gains can be achieved using a flat slide carburettor, though I was only looking at the different Dellorto body sizes.

Section Swept. Thank you for taking the time to put together a lengthy and informative reply. My comment that the bike is not used for trail riding or road use is really describing that I only do classic trials with the bike. When new the bike had to be set up as the purchaser could use it for trail riding or commuting requiring higher engine speeds for longer periods. I am only using the bike for easy classic trials with short loops and all sections ridden in first or second gear. I have experimented with 2 stroke exhaust design in the past which is a fascinating subject, but I am not proposing a change to the standard exhaust. Re air volumes between the carb and cylinder there is also no scope to vary this if the existing air box is retained. I haven't followed your logic that different carburettor sizes pass more air but somehow the velocity over the venturi remains the same. Velocity is proportional to velocity pressure so both must surely rise together? I realise the smaller carburettor bore will reduce top end, but I never use that anyway. So the question is whether gains can be made to bottom end and mid range by fitting a smaller carb as these are the rev ranges I use. At this stage it appears no-one has tried it. I may try the 22 Mikuni off my TY175 however I will need to make adapters and it will only be luck if the TY jetting suits the Fantic. Has anyone tried a Mikuni on a Fantic? The beauty of using a Dellorto is all the sizes 22, 24, and 25 have the same body dimensions and spigot sizes, as well as being compatable with the standard jets as a starting point. Regards, Peter.

Has anyone experimented with carburettor size on a rear kick Fantic 200? The bike is standard with no modifications. It is used in classic trials but not on the hard line, so doesn't need more top end power. I have calculated carburettor velocity for a number of air cooled trials bikes including Bultaco, TY175 and 250, TY Mono, and Gas Gas Aire, and all have the same velocity through the carburettor. The Fantic 200 carb would need to be reduced to 22 mm to match the velocity in all of the bikes listed above. 25mm is standard but the bike is not used for trail riding or road use. Has anyone tried a smaller carb to increase throttle response? Regards, Peter

Thanks for the replies and especially to Paul who provided a brilliant reply. I also sent an enquiry to America and got a very helpful reply there too. Spent this evening using the information provided and was able to start the engine. What I did is summarised below. I am advised the original coil was a single wire red Motoplat, and the Denso CDI coil I have fitted is a compatible replacement. It was also confirmed that the wiring diagram I posted is also correct. All measurements I recorded for the coil and stator were within 1 or 2 ohms of the values Paul provided with the exception of one. When measuring blue to blue Paul got 281 ohms. One mine each time I connected the meter I got around 100 ohms briefly then it went to no circuit. I had read on my trawling through the web that some Motoplat coils had this characteristic, so unsure whether my stator was good or bad I tried kicking the bike over with no plug. With each kick an AC volt meter connected across the two blue wires briefly showed a voltage between 10 and 17 volts. Next cleaned all the connection plug contact surfaces, then plugged the control box back in but left it hanging so no part of the case was touching the bike, connected the earth wire from the control box direct to the coil, sat the coil on top of the head, and disconnected the kill switch. Kicked the bike over and there was a good spark! Then bolted the coil into place in the frame and retried but no spark. Scraped paint off the coil mounts to get bare metal, put the coil in place (still with the control box hanging) and the bike started, so this problem is solved. Found the 1991 parts book on the web and this gives the plug as an NGK BP5ES. Is this still the recommendation? Also what is the standard idle mixture screw setting? Mine was 3 1/2 turns out but seems happier at 2.5 turns. So thanks to the help from this forum the bike is running and motor seems good, though bike needs the following new parts: tyres, chain and sprockets, rear suspension bushes/bearings, and a rear guard, plus sticking rear brake, and a number of small parts, but feels like it will be nice to ride. Thanks again, Peter.

Thanks for the reply. I have found names for people in UK, America, and Australia who can repair the units. Rather than send the whole system, (stator, control box, and coil) I was hoping to be able to identify which component is faulty, then replace or have repaired. At present I believe the coil fitted may not be compatible with the Motoplat control box so would first like to resolve if that is right. Regards, Peter.

I have just purchased a 1989 Gas Gas 327 Air Cooled Mono. It is fitted with Motoplat Electrics and has no spark. I have been unable to find a wiring diagram that looks like mine. The stator has a black, grey and 2 blue wires plus the yellow which is not connected. I understand the yellow is for lights but the bike has none fitted. The resistance of the spark plug coil tests OK but, from reading what I can find, should the bike have a different coil with both the green and white wires connected? Does anyone have an original wiring diagram and measurements for testing the components. Regards, Peter (in New Zealand) Motoplat System.pdf

You note your bike is on standard gearing of 10/41. In New Zealand our Gas Gas was supplied with 11/42. The taller gearing may smooth the response. Also make sure you have a slow throttle fitted. If a Domino throttle is fitted this would be a black tube under the grip. A slow throttle has full travel over around one third of a turn, while the fast throttle movement is the same throttle opening over a quarter of a turn. Hope this helps. Regards, Peter.

In the States go to Speed and Sport. These bars are unbraced and listed for TY175 and others. I am using them on my Greeves. https://www.speedandsport.com/index.php/parts/controls/handlebars-sammy-miller-classic-trials/ Regards, Peter.

Hi Tony, I have no experience with repairing fibreglass but am getting advice from someone who works with it every day. What I have learnt so far is that there are a number of different epoxies and polyesters. On my tank the wrong filler has been used which means it hasn't cured properly, resulting in the tank leaking. The previous owner fixed this by adding more filler until the tank no longer fitted over the frame tube. Luckily the incompatible filler softens (and the original fibreglass doesn't) by using a heat gun so first task is cutting and peeling the repairs off. regards, Peter

Mark, Thanks for the reply. Your bike is looking good. Unfortunately mine needs to be restored before it can be used, as it has suffered too many modifications in the hands of previous owners. I now have most parts I can identify are needed before I start, but I am sure there will be more once I start dismantling. Focus at the moment is repairing the tank which had part of the tunnel removed, plus a couple of extra holes cut in the bottom. These were then patched with aluminium and a resin that is not compatible with the original. At present I am cutting and peeling the repair layers off to get back to the original tank. Regards, Peter