colly Posted April 4, 2005 Report Share Posted April 4, 2005 my dads gas gas did the rev out sypetom. the inlet manifold was the problem, it was split, causing to much air to get in. if not that could it not be the read valves? Quote Link to comment Share on other sites More sharing options...
chris Posted April 4, 2005 Report Share Posted April 4, 2005 Wish you luck pumping up with a compressor! That why I said turn the regulator down, I don't know how high you can go with the pressure but I wouldn't presonally go any higher than 8 psi, can see seals poping out if you went to high. Quote Link to comment Share on other sites More sharing options...
heathy Posted April 4, 2005 Author Report Share Posted April 4, 2005 I've checked the inlet and can't see anything wrong with it, Although I think this is a carb problem, I will do a pressure test first to make sure. Thanks for everyones help! Quote Link to comment Share on other sites More sharing options...
ronm Posted April 4, 2005 Report Share Posted April 4, 2005 Healthy, I had an air leak problem on my Beta that drove me nuts for a while. I haven't ever disassembled a Dellorto choke, but on the Mikuni on my Beta, I found that any air that leaks past the seal where the choke rod goes into the carb has a direct path into the engine. This was a bear to find, since a lot of people including myself, don't bother with the choke circuit when cleaning their carb. Once I disassembled it, the possibility was obvious. You can seal it temporarily with a bit of grease. I certainly sympathize with you. Good luck. Quote Link to comment Share on other sites More sharing options...
heathy Posted April 4, 2005 Author Report Share Posted April 4, 2005 Thanks, I'll have to get another carb and try it on the bike to see if that solves the problem, I'll have to get it fixed soon as I want to have a go at the scott this year (must be mad ) and haven't been on the bike for a long time! Quote Link to comment Share on other sites More sharing options...
chris Posted April 4, 2005 Report Share Posted April 4, 2005 Really a very bad idea to use a compressor, due to the very small amount of pressure needed. Fair point but I would have though it was safer than using an bicycle pump in my case as you can set the regulator to 8psi, then I can pull the trigger in for as long as want and it won't ever go above 8psi. Quote Link to comment Share on other sites More sharing options...
ham Posted April 4, 2005 Report Share Posted April 4, 2005 Heathy, sorry I havent got a useful contribution to your problem but let us know what the dealer makes of your ' haunted' sherco ? Quote Link to comment Share on other sites More sharing options...
kevin j Posted April 4, 2005 Report Share Posted April 4, 2005 for pressure/vacuum testing, I have a 'MityVac hand pump with built in gauge. goes 30 InHg to +5 psi I think. About $40 in a kit. Neat little device. I would NOT depend on the pressure regulator-most likely quite fine, but the cost of failure is severe. Using the propane torch method (unlit) you could check for air leaks when idling. Two things stand out to me: 1. You said putting hand over the carb inlet shuts it right down. That would indicate any air leaks are not major and serious, or at least not enough for WOT running. 2. You also said (I think) the slide acts normally as it moves up 5 mm then takes off and pulls fully up to WOT condition. 5mm is quite a bit for an engine under no load, is it running quite higher rpm by then? It should not refuse to return on the spring, even in a runaway condition, unless the slide is being sucked against the wall, or if vacuum gets to the top of the slide area. Are the vent tubes in place properly? Is the slide and carb bore smooth and ungalled? cable etc have been addressed already. Here is a long shot: If sufficient fuel loads up in the crankcase bottom, then it goes to high idle, the high air velocity can indeed start picking up large amounts of fuel off the crankcase bottom. Closing the throttle should shut it down though, which you indiciated it does. the old Detroit Deisel 2 cycle diesel engines (with oil in the crankcase, but an air box around the cylinders) had one really nasty habit: if they idled a long time at cold temps, unburned fuel built up in the airboxes. The first time the engine was brought up to rpm, increasing air flow started picking up this puddled fuel and the engine went wild. Since diesels control by fuel injection, no throttling of the air at all, there was no control of the engine runaway speed. If the overspeed system was still working, it would pull the emergency air flap closed and maybe save the engine, but do other damage in the process. Your engine has a throttle on the air (or should). Either the slide, or putting your hand on it stops the air. Ideally of course, change the carb entirely to compare, but at least I would check the carb vent lines to the top, and change slide springs with another bike known to run fine. I think the vacuum is pulling the slide up, or that the spring is too light to bring it back down against whatever forces are pulling or holding it open. keep us informed a very interesting (to us as observors on the sidelines!) problem. kcj 5 mm is quite a large opening for an engine under no load. If the speed picks up to fairly high Quote Link to comment Share on other sites More sharing options...
heathy Posted April 5, 2005 Author Report Share Posted April 5, 2005 I think I have found the problem Today I took the carb off and blocked off all of the places air should be able to get in, (breathers, top, inlet) I then blew through the other side of the carb and saw bubbles coming from around where the piece of metal goes through to stop the slide moving (Picture below as I'm not sure what its called). Correct me if I am wrong but I am thinking the bike idles fine because that part is sealed as the bottom of the slide is touching the carb as soon as the slide moves, the seal is broken and an air leak occurs. Could this be the problem? Quote Link to comment Share on other sites More sharing options...
nigel dabster Posted April 5, 2005 Report Share Posted April 5, 2005 Does the slide move up and down the groove really smoothly? There shouldn't be any gaps in the seal around the guide. Just an observation but that carb looks dirty to me, if the outside is mucky whats the inside like? Have you set the float height as well? Jets for uk should be 33 pilot and 126 mains or near to that. Choke lever should sit down flat, tke off and clean assembly. The air leak shouldn't be there. Quote Link to comment Share on other sites More sharing options...
t-shock 250 Posted April 5, 2005 Report Share Posted April 5, 2005 As soon as you swap it for another carb, you will know! Is that not the first thing you should have tried? Quote Link to comment Share on other sites More sharing options...
nigel dabster Posted April 5, 2005 Report Share Posted April 5, 2005 You really should have breather tubes too. Quote Link to comment Share on other sites More sharing options...
heathy Posted April 5, 2005 Author Report Share Posted April 5, 2005 (edited) There aren't any riders around here that I know of with a bike with the same carb, I do have breather tubes i just took them off while I was checking the carb for leaks. The reason the carb is dirty is that I put some grease on the oring on the top thinking it could be that, it has been totally cleaned inside. The jets are: Main: 124, Pilot: 33 The choke does sit flat I just lifted it slightly so that the part could be seen. Edited April 5, 2005 by Heathy Quote Link to comment Share on other sites More sharing options...
nigel dabster Posted April 5, 2005 Report Share Posted April 5, 2005 Put some bubble gum over where you think the leak is then try it. Does the slide slide smoothly and the float height set right Quote Link to comment Share on other sites More sharing options...
james111089 Posted April 5, 2005 Report Share Posted April 5, 2005 I think the gas gas carbs are very similar try a mates gas gas carb its gotta run some sense better if its the carb! James Quote Link to comment Share on other sites More sharing options...
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