New around here, SV735 fast idle surging issue. Already tried all the obvious things

[bertsmobile1]

I appreciate the help for sure.

Agreed, most modern connectors are moisture resistant and not an issue. I'm more opposed to it on my cars as I don't want to have to clean any residue off my engines or risk having it discolor aluminum or composite materials as it burns into them. I'd mention what carb I have if I knew exactly LOL. I'll have to take off the airbox again to take a look. I see no PN stamped into it and the service manual I found for my engine shows a different image of the carb. They are similar but mine does not have the flat top piece secured w/ fasteners (See attached pic). KH-32-853-28-S is the PN for the Kohler SV735 according to what I've located. Every place I google SV735 carb I find this one I'm showing.

Tomorrow I may pull the shutoff solenoid again (had no cap, just a needle that closed off the jet) and see if it is in fact not retracting enough as that makes a bit of sense. It seemed to be free when I tore it down but I don't know if I'm hearing the solenoid engage when i'm keyon but I don't know that I paid any attention to that to be honest.

BTW, none of those kohler carbs are exactly what I have but the closest is the walbro LMK carb. It mentions a low idle fuel adjusting needle but unless it's under one of the welch plugs I don't have this either. Would you mind telling me when you find the kohler manuals? I've not found any manual for the 3285325-S. I found thisbut my Kohler carb isn't in there.

View attachment 45894
Dave

Kohler used Nikki & Keihin carbs \The latest manual number I have is # 32 690 01 Rev. D
Go to the Kohler USA web page then under customer support go to manuals
If you come to a log in page log in as "guest"
Then type in you model & serial numbers and it should bring up the operators, parts & service manual
32 690 01 Rev. D covers the engines SV 710 to 740 & SV 810 to 840

 

[TT_Vert]

Kohler used Nikki & Keihin carbs \The latest manual number I have is # 32 690 01 Rev. D
Go to the Kohler USA web page then under customer support go to manuals
If you come to a log in page log in as "guest"
Then type in you model & serial numbers and it should bring up the operators, parts & service manual
32 690 01 Rev. D covers the engines SV 710 to 740 & SV 810 to 840

Thanks,
I actually just got 32 690 01 Rev. H from there( i assume that is newer than Rev. D) and it shows 3 carb options (Nikki, Keihin and Walbro). Based on the exploded diags none of those are what I have on this thing. They all have an idle fuel adjusting screw near the base of the carb at the top which mine does not have.

Dave

 

[bertsmobile1]

Dave,
Well you are at the limit of my knowledge on this one.
The idle adjustment is not a fuel jet
If it is in the flange then it is a passage way metering jet that controls the volume of the idle air / fuel mixture that enters the carb throat.
Some have a removable idle jet that is usually under the plastic throttle stop , these pull out after the screw is removed then you blow then whole thing out from there.
A photo of your carb will help .
I am an independent workshop so tend to see mowers that are quite old or where the dealers tell the customer "can not be repaired but we will give you a good deal on,,,,, "

 

[ILENGINE]

You are thinking if terms of clean meaning there is no debris in the passages, but in this case could be a piece of aluminum corrosion that is part of the carb and will not be blown or sprayed out.

 

[TT_Vert]

You are thinking if terms of clean meaning there is no debris in the passages, but in this case could be a piece of aluminum corrosion that is part of the carb and will not be blown or sprayed out.

Thanks guys. I did blow out each passage both ways w/ air and liquid and given how clean this carb is (Looks new inside) I'd be hard pressed to think any aluminum debris or corrosion would be in there, or any for that matter. It's probably the cleanest carb I've torn down. Either way,I'm going to yank the carb again in a bit and get some pics and go through each passage again. I'm also going to test the fuel pump and that fuel shutoff solenoid a bit more as that could also cause my lean condition. These carbs are so simple i'm surprised I've not figured this one out yet. For comparisons sake the first carb I ever tore down was a quadrajet out of a 82 chevy van. In fact that's the first carb I ever rebuilt, with only the aid of the rebuild kit info which was very sparse. If i could figure that out I certainly shouldn't be defeated be a fricking 1BBL lawn tractor carb.

Dave

 

[ILENGINE]

Dave you are thinking in too big of components. This could be a 4 micron obstruction in a 8 micron passage that is cross drilled and then sealed off at the factory.

 

[TT_Vert]

Dave you are thinking in too big of components. This could be a 4 micron obstruction in a 8 micron passage that is cross drilled and then sealed off at the factory.

fair enough, not sure how I could rectify that then. Have the carb off and there is a plug Where most have an adjustable idle air screw sadly. I don't have spare plugs to knock this thing out but adjusting that would be a bandaid anyway as something is awry somewhere here. Will update in a bit.




Dave

 

[TT_Vert]

fair enough, not sure how I could rectify that then. Have the carb off and there is a plug Where most have an adjustable idle air screw sadly. I don't have spare plugs to knock this thing out but adjusting that would be a bandaid anyway as something is awry somewhere here. Will update in a bit.




Dave

Took it all apart again and used a stainless wire bristle to ensure the idle passages were not blocked and they were not. Then ran electronics cleaner (All I had handy) through each passage and saw it coming out perfectly fine. Same from every other passage. Also confirmed fuel pump and the fuel cutoff solenoid are perfectly functional. I did adjust the linkage a bit and the idle speed screw a tad and it's doing better but I still have that same fast idle surge I've always had. I actually have another carb coming to test and at this point I'm going to have to look hard and fast at these intake gaskets I think. PN of this carb is 3205328 and it's made by Kohler.



Dave

 

[TT_Vert]

sorry for the multiple posts, i'd edit if I could. I put on a cheap $40 amazon carb from presumably china and the problem went away after I did some tuning on it for other issue (Idle, AFR, etc.). Starts and runs perfect now. Idles steady at 1225 RPMs slow and 2950 fast, no more surging. I have ZERO idea where the issue is on this carb but there has to be some passage I cannot get to that is partially blocked. Every passage flows air/fluid just fine so I really am at a loss. Perhaps there is some bypass passage internal that I cannot see that is clogged. The original car ran fine, started well and never surged under load. It just drove me crazy listening to that surge while it was stationary at high idle. I suppose I could have just gone to low idle but that's just not me. I'd rather spend 2 days troubleshooting an issue that has zero effect on the function of the machine.

Dave

 

[ILENGINE]

Dave, don't feel bad, this type of thing happens every day in lawnmower shops across the world, and then customers wonder why we just replace the carb in a lot of cases instead of just cleaning and repairing the old one.