Hard restarts (hot) slight big off idle.

[JJinSC]

Ok, these issues just keep alluding me. Everything runs fine except for 1) slight bog from idle. It will clear out and not die on its on now that I have confirmed the a-pump nozzles are both spraying. It just hesitates now and then clears and goes. 2) hard restart after sitting for 15 minutes to a couple of hours. It was almost impossible to restart but I found that the pressure relief valve was not working properly. Cleaned it and got it working correctly and now I can restart it after sitting for 15 minutes to a couple hours but I have to keep blipping the choke. If I pull the choke and hold it too long it will die. I have to pull the choke and immediately release it about every two seconds to keep it running. After about a minute of doing that I can start giving throttle and as soon as it starts to bog and die if I blip the choke really fast it will grab and go. Once it goes it clears and runs fine.

Other than these two issues it runs perfect. Cold it will fire up immediately and run. Idles perfect. Has that slight hesitation off of idle but then runs perfect at all other RPMs. I am completely at a lost now what else to try. All lines replaced. New fuel selector valve. Vents working correctly. Carbs rebuilt twice. RAVEs in perfect working order. Water regular checked today. It seems fine.

Anyone have any other ideas?


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[Dr Honda]

Before I pass judgment....


I know you say that you blip the choke... but have you simply tried to hold the throttle down a little, as you crank? (warm start) If not... try it. Just hold (do not pump) the throttle open, maybe 1/8, and then crank. See if it grabs and then clears out.


If that's what's happening... then you are leaking fuel into the engine. Either the N/S are leaking, or the high speed check valve is leaking down.

 

[JJinSC]

I'll focus on trying that tomorrow. On vacation this week. However, it usually cranks right up by barely cracking the throttle. The problem is it will not stay running for more than a second or two unless I pull the choke and release about every two seconds. I have to do this for about 30 seconds to a minute before it will start taking some throttle. Once it starts taking throttle I can clear it out by pressing more throttle and blipping choke at same time. If I just throttle it will die. This is only on hot restarts after it sits for about 15 minutes. Cold starts are perfect. it will clear and run with just throttle.


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[Dr Honda]

is this an 800 or 951 engine?

 

[JJinSC]

787 (800)


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[Dr Honda]

The rotary valve could be getting warn.

If you take the carbs off... check the clearance.

 

[JJinSC]

Ok, will be checking leak down test on carbs tomorrow just got back from lowes and made me a pop-off/leak down tester. I'll check the manual for checking RV clearance. Is it pretty simple?

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[JJinSC]

One other thought. I'm still going to test for carb leaks tomorrow. But today just to test this, when I was done with a ride I turned the fuel selector valve to off and let it run out of gas. I let it sit for 30 minutes then turned the gas on and tried starting. The same hard starting (really easy start, hard to keep running) issue happened. Wouldn't this test eliminate leaking needle/seat?


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[JJinSC]

Ok, I finished carb leak down test by using hose pincher on the return line and connecting pressure tester to fuel inlet on the MAG carb. It held 15psi for 10 minutes and indefinitely. I guess the next step is to check the RV cover clearance. But before I do, wouldn't that cause hard starting period and not just hot restarts. Again, my issue isn't really a hard start or restart. It starts instantly and runs properly. The only issue is keeping it running if you cut it off And let it sit for 15 minutes to an hour. Then it cranks immediately and will only idle for a second or two unless I quickly pull and release the choke. If I do this a few times to keep it running it will then idle on its own but will not come off of idle without dying unless I do the same thing with the choke again.


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[Dr Honda]

If you HAVE to pop the choke... and then it will idle on it's own..................................


It almost sounds like the needle and seat is sticking. The choke pop's it open... and then after that... it's flowing.

Is the Needle and seat OEM??

 

[JJinSC]

Well the last time the carbs were done I didn't do them. It was during my rebuild so I had the technician do the carbs while it was there. I requested OEM parts and he stated that's all he ever uses. So I only have his word to go on but, he is a very good technician and has done a great job on everything I have had him do. He has a great reputation in the area too.

So what would I do about that , just order new needles and seats and replace them? Of course clean again as I go.


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[Dr Honda]

If you have the carbs off (or they are going to be off) pull the needle and seat. If it's OEM... there's a little stamp on it, that looks like a window... or a box, with a box in the corner. That's Mikuni's stamp. An aftermarket one won't have that stamp.

You could have the world's greatest tech... but if he used non-OEM parts... things never work right.

But I would check before ordering anything.

 

[JJinSC]

Ok, after testing everything today and finding nothing that should be trouble enough to cause any damage I think I'll just deal with the slight bog and nurse the hot restarts through what's left of the summer and then pull carbs after season to check everything. Trying to enjoy the rest of the vacation while the weather is good. It has been perfect here all week so far. [emoji41]


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[JJinSC]

Just for piece of mind. If the RV cover is out of spec, will it hurt anything to finish summer before checking/fixing?


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[CVFD1314]

JJinSC, I tackled a hard start issue involving fuel this spring, putting in all lines, fuel selector, filters, rebuilt carb, air check valves, basically a whole new fuel system. fired up and ran good and thought I'm good to go for the summer. then STILL had a hard start and came across the RV clearance on here. Mine was worn down pretty good and purchased a new one through SBT along with a new rotary valve. Got it put on and it fires up every time no problem. Once that RV gap gets over what it's supposed to be, it'll make for difficult start ups. I had someone tell me it won't harm anything running it like that, just more cranking to get it started. Just harder on the battery and starter.

 

[JJinSC]

Thanks for the input. That is most probably my trouble as. I still have the original RV and probably have over 600 hours on it. Fuel system is perfect including no leaks in carbs. I'm waiting till end of summer to check/replace.


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