dan williams Posted December 30, 2010 Report Share Posted December 30, 2010 I run VP C-12 so I also have no issues but I have also run CAM2 (Sunoco 110) race gas and noticed waxy residue on cold fuel bottles that doesn't occur with the C-12. Interesting note from the VP website FAQ: What type of 2-stroke oil should be used in C-12? C-12, C-14, and VP Red work very well with synthetic or petroleum based oils. However, bean oils will tend to separate below 35 degrees F. in fuels with a specific gravity of less than .730. Quote Link to comment Share on other sites More sharing options...
copemech Posted December 31, 2010 Report Share Posted December 31, 2010 Good point! I wonder what temp ranges the VP fuels are really designed for? I suspect a bit warmer ranges than the Avgas(cooler at altitudes). Aircraft do not like hot restarts on that stuff, either. Cannot really use it here in summer, but in winter seems fine. Quote Link to comment Share on other sites More sharing options...
geodet Posted January 1, 2011 Author Report Share Posted January 1, 2011 Very interesting discussion guys. I have tried all the suggestions, including the silkolene pro but the symptoms have not changed at all. i.e poor or no tickover, poor initial pickup, it fells like it wants to stall. once the engine is spinning it is great. Changing the pilot jet by a big jump did not change the symptoms which seems to point to something else amiss. Would incorrect ignition timing cause this type of problem? I am thinking too advanced. I have no experiance in this area so a little insight before I fiddle would be appreciated. Quote Link to comment Share on other sites More sharing options...
kramit Posted January 2, 2011 Report Share Posted January 2, 2011 Very interesting discussion guys. I have tried all the suggestions, including the silkolene pro but the symptoms have not changed at all. i.e poor or no tickover, poor initial pickup, it fells like it wants to stall. once the engine is spinning it is great. Changing the pilot jet by a big jump did not change the symptoms which seems to point to something else amiss. Would incorrect ignition timing cause this type of problem? I am thinking too advanced. I have no experiance in this area so a little insight before I fiddle would be appreciated. Now that the Engineers and Scientists have had their say, try some basics. New spark plug. Perhaps spray around the carb. and inlet areas with carb. spray cleaner to ck for vacuum leaks. Carb. Float level or Pinch/block the fuel line from the tank and see how the engine performs as the fuel in the carb. starts to run low. Can you exchange carbs. with another bike perhaps. Quote Link to comment Share on other sites More sharing options...
coriolis Posted January 2, 2011 Report Share Posted January 2, 2011 Had the same problem with mine from the day i got it. Runs fine one minute, staved of fuel the next. Im riding the 290 with the bigger 28mm carb. A buddy of warned me about the carb before i got the bike, as he had one on his beta. Seems the pilot is prone to blocking although i have no idea why. My friend kept going bigger on the pilot untill he had got rid of the problem. He ended up with a 45, having started out with a 33 ! He then found the real solution:- Put the carb in an unused, clean tin. An empty chocolate tin works well. Put the lid on Buy and fit a Keihin Not the ideal solution i know! Im thinking of experimenting with an OKO carb (Keihin copy). I was told they wont fit due to the CDI unit being in the way, but i had a sneaky look at Wiggy's bike the other day, and hes running a Keihin with a modified choke lever. Quote Link to comment Share on other sites More sharing options...
geodet Posted January 4, 2011 Author Report Share Posted January 4, 2011 Thanks for all the information guys but the problem appears to have been much more basic. A tiny piece of swarf lodged in the O ring seal of the pilot air screw was enough to break the seal. We are talking tiny here but sufficient to completly mess up the pilot circuit. Question is where did it come from? As I have read elsewhere on this forum it might be worth flushing out the fuel tank on your new Sherco before you use it. It would also suggest that the fitted fuel filter is not particularly efficient. At the time of writting the bike is running beutifully for the first time in a while. Quote Link to comment Share on other sites More sharing options...
coriolis Posted January 4, 2011 Report Share Posted January 4, 2011 Thanks for all the information guys but the problem appears to have been much more basic. A tiny piece of swarf lodged in the O ring seal of the pilot air screw was enough to break the seal. We are talking tiny here but sufficient to completly mess up the pilot circuit. Question is where did it come from? As I have read elsewhere on this forum it might be worth flushing out the fuel tank on your new Sherco before you use it. It would also suggest that the fitted fuel filter is not particularly efficient. At the time of writting the bike is running beutifully for the first time in a while. Yeah the stock filters are terrible. Mine actually partly melted. Must have some potent petrol ! Ive been looking for a nice inline filter on ebay, that is servicable. Found a couple of nice glass ones but both are too long, and the fuel pipe kinks badly. Im working on a little bracket to space the fuel pump towrds the front of the bike so i can fit a nice filter in there. Also, i was thinking of a secondary filter (a small throwaway one) between the pump and carb, but didnt want to restict the fuel flow too much so didnt bother. I did notice that Paxau has fitted a second filter to Wiggy's bike though, so ive ordered a few off ebay. Quote Link to comment Share on other sites More sharing options...
neo Posted January 4, 2011 Report Share Posted January 4, 2011 Ive been looking for a nice inline filter on ebay, that is servicable. Found a couple of nice glass ones but both are too long, and the fuel pipe kinks badly.Im working on a little bracket to space the fuel pump towrds the front of the bike so i can fit a nice filter in there. Also, i was thinking of a secondary filter (a small throwaway one) between the pump and carb, but didnt want to restict the fuel flow too much so didnt bother. I did notice that Paxau has fitted a second filter to Wiggy's bike though, so ive ordered a few off ebay. Maybe all this is one of the disadvantages of having a fuel pump sucking up sludge from the bottom of the tank. The older bikes have a basic filter in the tank and only really get the sludge after it's switched to Reserve. I've not had and extra filer on my bike for on my Keihin/OKO's (which do not not have a built in filter) but I had little with fuel blockages But just for future reference which fuel filter are you buying off of eBay?... Some time back I mistakenly bought a fuel filter (for another bike we have) that was made for a quad. It's an aluminium screw together thing that has a fine paper element inside...just like an 4 stroke engine oil filter. It would be great except for the fact that it's far too BIG for a Sherco....These things are hard to judge when looking at eBay photos. Best of balance. Neo Quote Link to comment Share on other sites More sharing options...
toofasttim Posted January 5, 2011 Report Share Posted January 5, 2011 (edited) Not sure I would call it "carb icing". That term is commonly used in aircraft and is actually a problem on warm humid days when the air at altitude passing through the venturi and then expanding drops the temperature of the incoming air to the point where moisture precipitates out into the carb throat and freezes. It doesn't happen in cold dry air. This reminds me. I recently read Stanley Hookers autobiography. Hooker was an engineer employed by Rolls Royce and Bristol aircraft. He was pulled out of retirement to get Rolls out of the RB211 fiaso in the early seventies. In the book he describes the problems Bristol had with the Proteus engine and specifically the icing problem. It only occurred in the tropics and put the schedule back over a year. The customers reasoned that if the proteus engine iced over the tropics it would be far worse over the north atlantic. Hooker argued that the air over the north atlantic was dry in relation to the tropics because the evaporation was far worse there. Edited January 5, 2011 by TooFastTim Quote Link to comment Share on other sites More sharing options...
coriolis Posted January 5, 2011 Report Share Posted January 5, 2011 Maybe all this is one of the disadvantages of having a fuel pump sucking up sludge from the bottom of the tank. The older bikes have a basic filter in the tank and only really get the sludge after it's switched to Reserve. I've not had and extra filer on my bike for on my Keihin/OKO's (which do not not have a built in filter) but I had little with fuel blockages But just for future reference which fuel filter are you buying off of eBay?... Some time back I mistakenly bought a fuel filter (for another bike we have) that was made for a quad. It's an aluminium screw together thing that has a fine paper element inside...just like an 4 stroke engine oil filter. It would be great except for the fact that it's far too BIG for a Sherco....These things are hard to judge when looking at eBay photos. Best of balance. Neo Interesting point about the "sludge". I may take this into acount when i attempt to make my carbon fiber tank ! Filters i am using are as follows: Disposable ones for use between pump and airbox http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=280544164562&ssPageName=STRK:MEWNX:IT Currently using this one between tank and pump. Its plastic, but its servicable and seems to work pretty well. http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=270665598238 This is the one i want to fit. Its a nice quality glass one, but is too long untill i make a bracket for the pump. http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=390209461950 Somebody suggested to me the other day that the airflow from the intake to the pump is restricted, and that an inlet spacer cures it and allows the correct amount of fuel to be pumped to the carb. Dont know how much truth there is in this, but he put a spacer in, and reports much better carburation! If anyone is interested in a spacer i can make them in any thickness. Stainless, alloy, or even titanium if you are concerned about the extra weight ! Neo, you mentioned you run keihins and OKO's. Im thinking of trying an OKO, just because they are cheaper. Any major performance differences ? Quote Link to comment Share on other sites More sharing options...
neo Posted January 5, 2011 Report Share Posted January 5, 2011 (edited) Neo, you mentioned you run keihins and OKO's. Im thinking of trying an OKO, just because they are cheaper. Any major performance differences ? From the old Dellorto?....yes a big differenced... more than any other mod I have done. When setup and running right I believe that the OKO can out perform the Dellorto in every way except one..."Consistency". I've spent many hours tuning and changing mine and most days the OKO is great but some days it's not so perfect. Although I would not go back to the Dellorto now (I have tried twice) because I'd miss the power zap! the OKO gives when it's needed. Here's a few things I'd recommend when fitting an OKO. For better stability (Consistency) go for a 24mm (smooth) or a 26mm (good all rounder)... do not get a 28mm or 30mm carb. Get a clear plastic bowl on the carb. It's not as deep as the metal one...this reduces any rubbing on the gear case. Use high octane fuel (98) and 80:1 fully Synthetic oil.... Castrol TT's good. With regards to rotation into the inlet manifold (engine side). Keep the carb as upright (vertical) as possible...Older bikes need to tilt the Rear brake resovior down to do this.... But I don't know about the newer bikes (2010 onwards). Because of the forward tilt the OKO has into the inlet manifold. Set the float level height to 20/21mm (not 18 as recommend)....stops the bike running rich on downhill runs. Use a JJH or GJH (even smoother) needle. The rest is in past threads on this forum. I'm currently working with a higher cut slide too....But I'll report on that when I've finished testing it. Having said all this .... Isn't your bike running a Dellort VHST??? ... If so I wouldn't bother. I've bought a VHST and might venture that way when I am bored one day .... I stuck it on for a few days. It was running rich and lacked power but I had no other pilot or main jets to try at that time. But the write-up's say they are good carbs. If you don't already have a VHST then an OKO would be a lot cheaper and a good way to go. I like the glass filter....might invest in one myself...do you think there's enough room down there? Let us know about the CF Tank ... that sounds like the business to me Best of balance. Neo Edited January 5, 2011 by Neo Quote Link to comment Share on other sites More sharing options...
coriolis Posted January 5, 2011 Report Share Posted January 5, 2011 I like the glass filter....might invest in one myself...do you think there's enough room down there? Let us know about the CF Tank ... that sounds like the business to me No where near enough room for it at the moment. That is why im going to mount the pump on a bracket that positions it further towards the fromt of the bike. Paxau has done it to wiggy's bike, but i didnt see how he did it. CF tank is only in the thought/design process at the mo. Deciding on the best way to fabricate it. Joining the two halves is the main sticky point. Gonna mock one up in Glass fiber first. Will post the results no doubt. Also toying with the idea of a full titanium frame! I agree about the normal delorto carbs. Super reliable. I dont feel that way about my VHST though, and could do with some more top end at times. Quote Link to comment Share on other sites More sharing options...
neo Posted January 5, 2011 Report Share Posted January 5, 2011 (edited) I dont feel that way about my VHST though, and could do with some more top end at times. Now thats very interesting feedback....and kinda confirms my suspicions. A CF tank would be awesome (don't forget the baffels ) ... but a Ti frame would be a real challenge...I'd guess you'd have to bash it on the rocks a lot of times to test it ... can I be your beta tester Best of balance. Neo Edited January 5, 2011 by Neo Quote Link to comment Share on other sites More sharing options...
copemech Posted January 6, 2011 Report Share Posted January 6, 2011 Will any of this improve your riding? Quote Link to comment Share on other sites More sharing options...
coriolis Posted January 6, 2011 Report Share Posted January 6, 2011 Will any of this improve your riding? Im confident it will take me from novice to world championship status! I just like messing about to be honest, and everyone likes a bit of bling dont they ! Quote Link to comment Share on other sites More sharing options...
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