Bertie 314 #1 Posted July 23, 2019 So I took the top off the carb and found a spring and ball lurking in the bowl... on the pic one is obviously a needle valve sitting with the float ... the other I thought could be another valve? Where does it go guys thoughts appreciated Share this post Link to post Share on other sites
lynnmor 6,762 #2 Posted July 23, 2019 I think you might have a newer than 1995 spec G carb and that is a check valve for the accelerator pump. Check your number plate and also verify if it has an accelerator pump. Those carbs are to be replaced rather than rebuilt, so be careful with gaskets. If you do have the spec G, I would toss it for an older model. 1 Share this post Link to post Share on other sites
Bertie 314 #3 Posted July 24, 2019 (edited) 7 hours ago, lynnmor said: I think you might have a newer than 1995 spec G carb and that is a check valve for the accelerator pump. Check your number plate and also verify if it has an accelerator pump. Those carbs are to be replaced rather than rebuilt, so be careful with gaskets. If you do have the spec G, I would toss it for an older model. Thanks, It does have the accelerator pump. Any ideas why it would be laid in the bowl as I presume you would have to strip the pump to gain access to the check valve? As for replacing with an older model there are none in the UK and can't find another in the USA willing to post to the UK at the minute 👍 Edited July 24, 2019 by Bertie Mistake 1 Share this post Link to post Share on other sites
lynnmor 6,762 #4 Posted July 24, 2019 5 hours ago, Bertie said: Thanks, It does have the accelerator pump. Any ideas why it would be laid in the bowl as I presume you would have to strip the pump to gain access to the check valve? As for replacing with an older model there are none in the UK and can't find another in the USA willing to post to the UK at the minute 👍 I don't remember exactly how that thing goes in, its been a long time. I see some aftermarket carbs for cheap on fleabay that ship worldwide and some used ones as well. Order a kit if you get a used one that includes the welch plug, then use only genuine Onan gaskets for the manifold to engine. 1 Share this post Link to post Share on other sites
richmondred01 2,202 #5 Posted July 24, 2019 I have two left. Both were taking off running 416. pm me interested. 1 Share this post Link to post Share on other sites
Bertie 314 #6 Posted July 24, 2019 PM re the carb ... sent 👍 Share this post Link to post Share on other sites
Bertie 314 #7 Posted April 21, 2020 On 7/24/2019 at 5:06 PM, richmondred01 said: I have two left. Both were taking off running 416. pm me interested. So nearly a year ago I purchased a carb from you which I recently fitted. Time laps due to moving home etc but just to say a big thank you I corrected a few other issues fitted the carb and it now runs sweet no surging all sorted.. cheers Des 👍 Share this post Link to post Share on other sites
richmondred01 2,202 #8 Posted April 21, 2020 Glad to help. 1 Share this post Link to post Share on other sites
onanparts.com 178 #9 Posted April 25, 2020 On 7/23/2019 at 4:47 PM, lynnmor said: I think you might have a newer than 1995 spec G carb and that is a check valve for the accelerator pump. Check your number plate and also verify if it has an accelerator pump. Those carbs are to be replaced rather than rebuilt, so be careful with gaskets. If you do have the spec G, I would toss it for an older model. Since this thread was updated I'm going to correct some misinformation. The later style carbs are NOT to be replaced rather than rebuilt if that option is desired. Kits with gaskets are readily available for them. It's not necessary to be careful with the gaskets. The 146-0657 repair kit fits both the accelerator pump style carbs and many of the early style carbs that came before. 146-0658 is the kit for the accelerator pump. The early style carbs are the better choice, but replacing a newer style carb that can be put back in service with a good cleaning and using repair kits for a minimal cost, is not the best economical approach. An early style used carb is still going to require the same cleaning and 146-0657 kit in most if not all cases. Pictured are the two repair kits. Share this post Link to post Share on other sites
Handy Don 10,563 #10 Posted November 3, 2020 Dived into a 400 hour P218 that just wasn't running right. Needed partial choke all the time and didn't respond to the the throttle in any meaningful way. I could see the governor moving the throttle and also see the squirt of fuel from the accelerator when it called for more power. It wasn't exactly "the surge" but more of a "wave". The PO told me he'd "cleaned the carb" using an ultrasonic bath and that sounded ok as far as it went but looking at the overall maintenance level of the machine (poor!), I suspected something hadn't been done correctly. (Spoiler alert: yep, a pretty significant something) Based on advice from @lynnmor I got an OEM gasket kit, fuel-proof sealant (to reseal the intake manifold if necessary), and started in. Got the manifolds off. No leaking gaskets, intake manifold seemed still tightly sealed. A bit of carbon in the exhaust ports but more like a thin coating than a serious accumulation. The Intakes have a bit of gunk around the base of the seats but again, nothing really striking (clearly it needs an oil and filter change--on the way) Get the carb on the bench, it looks pretty clean and the choke and throttle plates seem to move fine with no play. Next get ready to start in with cleaner in all the passages. Go to remove the idle jet and...lo and behold! The Welch plug directly above the idle jet adjuster screw is just NOT THERE! No wonder this beast would not run happily! There is probably a good story about how it came to not be there but it'll remain a mystery. So I've finished cleaning all the rest of the carb and am now waiting for the plugs I've ordered to come in. Betting that I found the culprit and I don't have to go further into this relatively young carb. Meantime I'll clean up the top of the engine, pull the valve covers, and check the valve adjustment (since I'm in this far and I have the gaskets at hand). Thinking I'll paint the valve covers as well, since they look a bit rusty. I'm also replacing the fuel pump because the PO managed to break off both of the "in" barbs (yet another mystery) and had hacked a clamp to hold the hose onto one stump and had put a screw in the other. Originally I suspected that the pump wasn't getting enough fuel to the carb due to the "intermittent spurt" fuel flow visible at the fuel filter--that it was sucking air--so i preemptively ordered a new pump. BTW, connecting the pump's pulse hose is a pretty nifty trick as it comes out of the blower housing with very little slack! Onward! Share this post Link to post Share on other sites
lynnmor 6,762 #11 Posted November 3, 2020 I had that welch plug come out on its own, the engine surged considerably. I hope you are opening the carb and doing a complete cleaning, all those small passages can be blasted with a spray can of carburetor cleaner that has a straw, wear eye protection. You mentioned a "squirt of fuel from the accelerator", is this a carb with an accelerator pump like the one pictured in a previous post? If it has that piece on the side that is held with 3 screws, then that is the accelerator pump that is only on 1996 & 1997 engines. Those "emissions" carbs had a very small welch plug over the idle mixture screw unless someone removed it and added the longer screw. Share this post Link to post Share on other sites
