Frustrated with my Bendix Carb.

[Cabindweller]

I have had about all I can stand of the Bendix carb on my 74 600. I know thease older sleds don't run as well when it is warm out side, but mine dosn't run worth a Sh%t when it is warm. It is ok for the most part if it is colder than 20 out side. But if it is warmer than 20 it my 600 gets very temperamental. I have been through this carb with a fine tooth comb and reacently replaced the high speed needle with a NOS needle. There was slight improvement but still it will bog and falter after a few high speed runs. I followed the tuning procedure from the faqs section and so far that has yelded better results than the manual. In the end there just seams to be something wrong with the carb. For a test, I put a HD tillotson on there a few months ago and wow, it woke my 600 right up. Out of the hole was a huge improvement. I never kept it on there long enough to dial in the top end, but it was no worse than the bendix as it was. No matter how good I can get the Bendix set it allways is lacking out of the hole, even when it is cold out. I can get it to perform decent in the midrange, but it will start to bog and falter after a few high speed runs on a day above 20. I have new lines all the way around the fuel pump was new last year, the filter was new last year and still is good. I will say that when it gets warm I start seeing allot of air bubbles in the lines including prior to the Fuel pump. I keep a close eye on my plugs and I can see changes in them depending on how I happen to have the carb set that day. I would like to keep the origainal carb on the sled but I apparently am not smart enough to tune it, or figure out what could be wrong with it. I have been thinking that I should reroute my fuel line. At the moment it runs under the motor. One other thing, I never had the heat deflector untill about a month ago, but installing one made no difference. If I cant figure this one out I think I will put a Tillotson on there next year. Any help or ideas? I wish I knew someone that knew how to tune and trouble shoot this with me.

Thanks for reading my rant
Jerry

[400brian]

Jerry

Did you insulate the heat deflector? Leave about an inch all the way around to seal the engine console. Wrap the lines with insulation from the heat deflector to the battery box. I'm not saying its going to cure the problem, and you could always go to a Walbro.

[joshua16]

jerry dont feel alone my jdx4 special still has the bendix carb and it runs like a piece of sh#t to quote you.the sled runs very bad in 30 degres or higher it idols bad and lacks power but when its colder i can get 55mph than i run out of field and to quote you again im not smart anough to tune my sle ds carb i mean im getting sick of loosing races to my younger brother and his scorpion.joshua

[Cabindweller]

Brain
No I haven't insulated the Heat Deflector or the line. I will give that a try. Is that insulation available through McMaster Carr?
We are fast running out of cold days and snow. Yea I know a Walbro would be more correct for the sled, But a Tillotson such as the one I borrowed didn't require a return line and my tank dosn't have one. Not that it would be to hard to find the other style tank fitting. It seams most everyone I know prefers Tilliotsons over Walbro and Bendix.

Jerry

[Cabindweller]

Joshua

I know what you mean, I get smoked out of the hole by my buddys 69 olympic with a 399 twin. Not that the 600 was a performance sled but it is still fun to line them up once and a wile. All I know is the Tilliotson Carb woke my 600 up. Night and day difference out of the hole. No bog or hesitation what so ever. Mine will do 55 on a good day maybe 60 on a great day.

Jerry

[400brian]

My first thought is that the carb is too rich. Performance degrading as the temp comes up is common.
My X8 will spit back through the carb and run poorly in general when the temp gets up around 35.
I lean the high speed needle until it runs decent, then I run it with a bit of restraint. The important thing is to richen it back up when the temps drop, or you'll risk burning a piston.

[S_Kyle]

Might not be the correct thing to say but, have you though of switching to a walbro. A friend switched his bendix's to walbro this year and we have alot better luck with them since the switch. I have always had trouble with the bendix carbs for what ever reason but, I have very good luck with them on several different sleds and think they are a great carb.

[Cabindweller]

It just feels good to know I am not the only one who has trouble with the Bendix carb.

Thanks for the responses guys.

Jerry

[joshua16]

jerry let me now if you get that bendix working right maybe i could win a race or two

[Cabindweller]

Joshua,

I will try a few more things before I give up on it compleatly. One of the things I might try is getting a replacement Bendix or two from my local sled salvage yard. The owner there told me that sometimes you just got a bad carb. I would like to mention that I did put a Mikuni off from a 76 Cyclone on it just to see what would happen. Wile it would idle, it was way to rich to throttle up, and would just bog when you gassed it up. I would be interested to know what jetting would be in the ballpark to get a cyclone or a liquifire carb to work on there. I have a few 76 liquifire carbs laying around here too.

Jerry

[400brian]

I had a Mikuni on a 340/5 for a while. It had a 250 main in it to start, and was WAY too rich. Somewhere between 200 and 220 might be correct. Start fat and work your way leaner. I found out he same thing, that the Cyclone jetting was way too rich for this app.

[Cabindweller]

Tried Something easy and obvious today. It is 24 out today. I made a few runs and the 600 ran wonderful untill it warmed up. Then bog and die. It seems to be starving because I need to prime it to get it started again. So I went home and looked things over. There was the usual air in the lines but only from bellow the engine and the pump and carb. There was no air in the lines from the tank, filter and up to and bellow the motor. My concern was that there might be a leak at the T for my primer. So I had to remove the engine cover and panels to investigate. With the panels off I started the engine and before long the bubbles disappeared. I then proceeded to go for a few high speed runs and wouldn't you know it, it bogged a little at first, but I put on a few miles without any trouble at all. So it comes down to a heat issue. To bad we are running out of winter. I think I am going to be able to work this out.

Jerry

[400brian]

Insulate the lines under the engine, get the rest away from the exhaust, and seal up the heat deflector with the same duct insulation, and you should see an improvement.

[Cabindweller]

Yes Brian You are right, I need to do something to keep the heat out of the area of the carb. It is 35 here today. I ran my 600 for a mile or two with no plastic and it ran great. I re-routed my fuel lines a little to try to keep them away from heat and put all the plastic back on. It wasn't long and it started to act up. This is not a carburator issue at all, but more of a heat management issue. With all the warm weather we have on the way it looks like I am done riding her this year. But I have all summer and fall to get my hands on and add insulation. Hind site is 20/20. Now that I have studied this issue it makes complete sense that performance degrades on warmer days. That compartment the carb and airbox is located in, is not well ventilated and collects a lot of heat. Knowing the sensitivity of the carb to air temp it all makes perfect sense. Just for an example the night I put my 600 back together and tuned the carb It was inside a heated garage. It ran like a swiss watch sitting in the garage. I opened up the garage door and drove the sled outside into the 15 degree air. Before I got the garage door shut the 600 quit running. I had to readjust the idle screw all over again. If I was a hacker I would cut a hole in the side of the plastic and run the rubber intake hose out the side of it. Just thinking of ideas to get some cold air in that stuffy compartment and into the carb. Hope if nothing more i hope this thread helps others dealing with similar troubles.

Jerry

[S_Kyle]

I know it is not stock but has anyone tried to put vents in the plastic? If you found small flexible vents you could maybe attach them to the centre plastic peice to vent the hot air.