Another exhaust system installed complete. Front pipe is the smaller bore Thruxton swept back item with my repaired track day silencer on the back end.. It was necessary to change the front pipe as my alternative silencers all have the higher ground clearance bracket. If I fitted these silencers to the standard front pipe there is about 3/4" difference in the silemcer mounting holes. With the later pipe in place I can switch between The known but repaired original and then slip on the brand new item from unknown manufacturer. Interestingly the swept back pipe is approximately 4 inches shorter than the venom standard pipe.Perhaps the combination of small dia pipe and shorter pipe may alter resonance Hopefully the weekend provides the opportunity to get out and hopefully find a difference.
Have you actually measured the main jet..? Years ago I ended up with a drilled out main jet..
Also you should be (for this part of the tuning) be at wide open throttle, this eliminates the needle and needle jet. And I do suggest you put a clear tube on the carb drain and watch the fuel on the dyno. Float level within a very large range will not have much effect at wide open throttle, not this much.
And as you are on a dyno, what instrumentation does it have..? That instrumentation should tell you a big tale.. if there is nothing, then find a different dyno... Good Luck.. Ron
Ron and Magnetoman, yes the Dyno is a little down on bells and whistles, Does not have mixture analysis probe and I am not sure about ignition monitoring. What should a good dyno offer? All of the vintage racers in the area use this guy with good result.Perhaps because this equipment is very thin on the ground in this area. On the main jet, I ended up with a bag of new AMAL 330 main jets when I bought a small stock of velo parts.. so I will verify with #53 drill. I do have a bottom cap with clear line attached which will go on the dyno run when I can arrange to go for my freebie. In the meantime I could install it , make sure the bike is vertical and run it in the garage to see if the level moves around relative to the dot on the side cover.This would not really simulate a full load situation but might point out a fuel supply issue. What do you think? I still have to fit in a an actual test of the newly installed exhaust system.(Little medical issue getting in the way at present) We have a couple of Kilometres of down hill slope near us and that should suffice for a test.
This would not really simulate a full load situation but might point out a fuel supply issue.
Which brings to mind the vent in the fuel cap. If it is partially plugged it will restrict fuel flow. I didn't think to mention this earlier but it's a simple one to deal with (if you haven't already done so) and then be able to eliminate as a possibility.
On the fuel supply side , I had checked the cap vent even opened up the hole inside and out. Also ran the bike with two taps "on". Pulled the fuel lines and checked flow from the taps. pulled the taps checked those filters and had the inside of the de-rusted. replaced the filter on the carb. I did take .012" off the float needle housing to lower the fuel level to make it line up with the dot on the cover. As I said before I may incremetally add shims back to see if a slightly higher float level changes anything . The carb does not exhibit any flooding tendency I.E no evidence of out of control fuel so I assun=me the float and float needle combo are doing their job.
Rob, When you checked the valve timing, did you just check the intake opening? On my velo, if I set the timing to the intake opening, the intake closing and the exhaust opening and closing were all off. I adjusted it so they were all close to spec and the intake opening was off. Bike was much better. Had a similar problem with an a65 that wouldn't run right. Turned out to be a bad cam from the factory. The last valve I checked was the primary side intake; it was opening 20 degrees late and closing 30 degrees early. Moral of the story is check the timing of each valve through its complete operation.
Hi guys, sorry about the long absence.I managed to buy a new fishtail supplied originally by Dave Smith. Fitted it today and immediately the bike sounded much more crisp and velo like. Took it out for a few miles in the autumn sun, mid range is even stronger and sitting upright going up an incline she was into the mid 80"s. The also seems to have less vibration. Good enogh for me! Not sure if Dave Smith had these fishtails made slightly differently but this one certainly performs much better than the other two. Still using the smaller diameter swept back pipe. many thanks for all the input. I have the offer of a free dyno check again but I do not really care about the Hp reading just wanted the bike to be able to rev out in top the way it's makers intended.