Squidproquo

So all back together with 127 main jest (all I could find locally) and hey presto, it makes big power now. It still might be a bit rich at high rpm but it's close. I have a set of the stock jets (117.5) that I may try at some point or I might take the top back off the airbox or remove the inner baffle ring. Now I need to find somebody with a stock Venture around here to see if the VMax motor is stronger or not in this configuration.

So since stock 1st gen Venture main jets are 117.5 and I found my bike is running 155's I think I may have found my smoking gun for my WFO throttle issues.Even though it's a VMax motor I'm going to start off with 117.5's because I think the exhaust is going to be the limiting factor. I may need to go up more due to better VMax flow rates but we shall see. By most accounts the 152 stock VMax mains were already too rich in that bike.

OK so the carbs are out and apart and the results are pretty inconclusive. The diaphragms look to me to be fine. The bowls are clean, the main jets (my prime suspects) look clean and are #155 . (what was stock?) Needles are on the third groove from the top. I got all the jet-like things out of the jet block and nothing is plugged. All-in-all it looks like a good clean set of carbs. My only question is what is the stock main jet size. I'm not sure if these carbs are off of the Venture or the VMax. Again the symptoms: It kind of acted as if the main circuit was too rich. When I whack it wide open it would kill any increase in power, even at lower RPM and would never pull more then 4500rpm with the throttle wide open. Closing the throttle a bit at that RPM felt like it was about catch and give some power but only barely for a second. The lower part of the rev and throttle range felt great. My gas milage is not good. 25 mpg over the few tanks I have had it running. I suspect my next adventure is going to be the ignition system. I might be able to convince myself that the added combustion pressure at those throttle openings and RPM may be straining a weak ignition system into failure under those conditions. Since the carbs look ok (to me anyway) that's about all I have left. Can someone point me to a parts list to convert to coil over plug? I'm assuming that ignition system is Venture or a hybrid of Venture/VMax. Is there a replacement for the ECU? I will go searching the forum(s) but I have seen some ideas but if there is a conclusive solution I'd like to hear it. One last thing I might consider is that the exhaust has the infamous collector rattle at idle. Could the lose baffle be consistently blocking the output enough to cause all this?

Well I got enough apart to get the "tops" off the carbs and have a look at the diaphragms and slides and everything seemed in order. No rips or funkiness in the rubber, the c-clips are set on the third groove from the point of the needle. Would I be correct that this is likely a decent ballpark for the needle height on a bike with stock exhaust and airfilter/airbox? Next I guess I should pull the airbox and see about getting a look at the main jets and the content of the float bowls.

So I came upon this old thread looking for advice or needle settings. For the sake of posterity (like me) I would like to add that what the shims are for is to enable a needle height that is 1/2 of the way between two slots in the needle, thus giving an ability to more fine tune the needle settings. If the shim/washer is above the c-clip it's merely being stored there. If you use it below the c-clip you have raised the needle 1/2 of a step.

Greeting to all here, I'm a newbie to the Venture scene but I have ridden for about 40 years and I'm a life-long Yamaha fan (FJ1200, 550 Vision, FJR1300, FJ09, among others) and I do most of my own work. I have been working on this new project bike I just picked up, a pretty clean 83 Venture with a VMax (!) motor of unknown vintage, transplanted by the father of the previous owner, that doesn't seem to want to make power at large throttle openings. I'm suspecting the carbs but I haven't gotten into them yet. The bike came to me without an airbox cover so I got off of Ebay and it anything, adding the cover made it worse. It runs OK at part throttle but when you open it up over 4000 RPM and expect that VMAX thing to start happening it just doesn't, and it starts to misfire like it's lean. It wont pull hard or really at all at large throttle openings. I think the carbs are from the Venture but I cannot be sure. I don't know if the bike was rejetted after the transplant, and I'm not sure if the engine has Vmax or Venture cams in it. I did get a big box of valve shims and lifter tools with the bike. Also I just refilled the tank for the first time and I got 100 miles out of 4 gallons of gas. Not great but I'm unsure if this points to something or not. So if I gather from all the searching I have done in the forum, spanning a couple decades, that the CV diaphragms tend to go bad and that fits the lean misfire thing if they are leaking and aren't letting the needle rise out of the jet making it lean. My forum search is not yet complete but if anyone has the link to where the latest/best source for the best carb kits and diaphragms I would be grateful. I will be pulling the airbox tomorrow to try to assess the state of the slides and diaphragms before tearing the carbs off. I'm also open to this being an ignition problem but it sure does feel like carburation. If there is something I've missed that happens to these bikes that causes this problem I could sure use that news too. After I get this resolved it will be time to do something about those linked brakes. Wow what a bad idea, at least as it is now on this bike. I already have all the parts (forks, R1 brakes, etc) for that except the lines. But I have to make this thing GO better before I worry about making it STOP.