# CUMMINS ONAN RS17A standby generator valve clearance adjustment



## storysRVIgo (Jul 18, 2021)

I have searched all CUMMINS ONAN documentation I have and can find online. Nowhere can I locate the engine valve clearance adjustment procedure. 
My home standby generator is specifically the C17N6H model. Or RS17A. Which is one of the confusing things in the CUMMINS product line as to which model number to refer too but I believe a procedure for the 13, 17 and 20 models will be the same. 

Getting support from the local CUMMINS facility via email or direct phone call is impossible I can understand email perhaps not monitored regularly but phone calls go to an automatic attendant and regardless of path I take to leave a recording, never a call back. National office politely refers me to contact the local sales & support. Exactly what I am trying to do. The egional rep I worked with from that office retired, otherwise I'd chase this through him. 

Great generator so the block wall to support mystifies me. Short of driving 40 miles to "tackle" someone there (anybody home?), I am fully capable of doing this myself. I have spare valve cover gaskets. If I can just get the factory procedure for this series of genset, that would be terrific.

Gene


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## iowagold (Jan 22, 2020)

so what do you need?
the valve clearance spec?

as for setting the valves
remove the spark plugs.
remove the valve covers
role over the motor by hand till the lobe of the valve you wish to check is 
up and not making pressure on the valve stem.
check or set the clearance.
repeat for all of the other valves.
note the intake will be closer than the exhaust.


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## storysRVIgo (Jul 18, 2021)

iowagold said:


> so what do you need?
> the valve clearance spec?
> 
> as for setting the valves
> ...





iowagold said:


> so what do you need?
> the valve clearance spec?
> 
> as for setting the valves
> ...


Hi Paul, Thanks for the quick reply. I should have been a bit more specific. For valve lash position, the method you describe will certainly get me to that position. If CUMMINS-ONAN documents the positioning procedure like other companies, they usually state it in terms of crank the engine manually in the normal rotation direction until TDC or some distance away from TDC to position the valves in their closed positions for that cylinder to be checked or adjusted. I can find valves-closed position as you describe for an individual cylinder too, of course. I should have been more specific in that besides whatever procedure the factory defines to arrive at valves closed position, then what is the valve lash clearance specificaton between the stem and the rocker. That usually is different distance for Intake versus Exhaust but without the spec, I can only guess that it would be similar to other small engines; something like .004 to .006 for the Intake and .005 to .007 for the Exhaust. But what does CUMMINS-ONAN specification say? Oddly that is the numbers that I cannot locate in all of the manuals or online resources I have checked. I imagine I have just skipped over this somewhere. Do you know the numbers they would spec? Without removing the cabinet panels, I cannot see the engine model (I think OSJ999G is used in RS17A/C17N6H) or serial number yet. 

Gene


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## ToolLover (Jan 13, 2020)

I found this: Cummins onan valve clearance - Free Pdf Manuals Download | ManualsLib
Adjusting Valve Lash - Onan HGJAB Service Manual [Page 72] | ManualsLib
Dig around and you may find the info you need.


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## iowagold (Jan 22, 2020)

in sae inches they are calling for .004 or 4 thou...
that is as cold... and for both valves
that might be a bit on the tight side for me!
.006 or 6 thou intake
.008 or 8 thou exhaust
is what i like..
that leaves some room for the engine to heat up!

measure where it is right now before you adjust it.

and i always look at the settings when the engine is hot to make sure it still has a thou or two as Hot.

you can burn a valve it is is too tight...
i would rather be a bit loose than too tight!


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## storysRVIgo (Jul 18, 2021)

ToolLover said:


> I found this: Cummins onan valve clearance - Free Pdf Manuals Download | ManualsLib
> Adjusting Valve Lash - Onan HGJAB Service Manual [Page 72] | ManualsLib
> Dig around and you may find the info you need.


Thanks but I have been digging around Internet as well as my cummins.com login for information that pertains specifically to my engine. I have placed a message to CUMMINS but its iffy that they will respond. Our rep at local CUMMINS facility retired and literally nobody else answers the support line there. While I might try a sales number, it seems I am destined to make the 52 mile drive to confront someone face to face with my question.

This morning I removed access panels and find that the engine identification is visible with the removal of the plate for oil changes but so far, this information has not helped with my Internet research, including at cummins.com


iowagold said:


> in sae inches they are calling for .004 or 4 thou...
> that is as cold... and for both valves
> that might be a bit on the tight side for me!
> .006 or 6 thou intake
> ...


Excellent Paul, thank you!
I probably will pull the access plates next week and of course check the clearance, assuming right at TDC and see what I come up with. Ideally all is well and I don't have to adjust anything. 

Regards,
Gene


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## iowagold (Jan 22, 2020)

most of the time they are dead on perfect.
yea take your time and it is worth the effort for sure!


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## storysRVIgo (Jul 18, 2021)

Cummins "national" support got back to me today. There is indeed a 21 megabyte Service Manual in PDF, document # A062J683 for the RS13A-RS20AC aka CxxN6H generators (Type B noted) that has the definitive Engine Valve Clearance procedure and valve clearance specifications. I can tell you that I cannot find this document anywhere on the Internet, including my access to Cummins and Cummins Quickserv Online sites. I am not sure I can act as a medium to post the document Cummins sent to me but this is THE document publication number that has the valve clearance procedure, and the Intake and Exhaust valve clearances for Ambient and Hot. Even if I re-write their text and chart to post here, I hesitate to do so because if the procedure is not followed exactly, bending a valve or even destroying an engine can be the result. I therefore recommend that any home standby generator owner, utilize Cummins factory techs to check, and if actually needed, adjust your valves. 

If it was even permissable to post a copy of this large, 21mb Cummins document or a 3 page excerpt from it where this procedure is located, I would place it in a Files section but I do not see that this forum has a Files section. For myself because of years of experience on a lot of engine types, I feel comfortable to do the check and if need be, adjustment process. If any of you are so inclined to do this yourself, I'd contact Cummins and ask them for a copy of this A062J683 manual. And please know that it references "Type B" models. I have not verified that Type A which is what I have, follows the B valve adjust procedure even though the reply to my Cummins question related to my Type A unit. At this moment I do not know what the difference is in the Types.

Gene


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## tabora (Sep 6, 2018)

storysRVIgo said:


> There is indeed a 21 megabyte Service Manual in PDF, document # A062J683 for the RS13A-RS20AC aka CxxN6H generators (Type B noted) that has the definitive Engine Valve Clearance procedure and valve clearance specifications. I can tell you that I cannot find this document anywhere on the Internet


You mean this one?


https://www.electricgeneratorsdirect.com/manuals/cummins-power-generation-2a229eee67dedc1603d2d051a3b9d5af.pdf


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## iowagold (Jan 22, 2020)

cool tab! well done!


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## storysRVIgo (Jul 18, 2021)

tabora said:


> You mean this one?
> 
> 
> https://www.electricgeneratorsdirect.com/manuals/cummins-power-generation-2a229eee67dedc1603d2d051a3b9d5af.pdf


Tabora,
Yes; you found it. It is an earlier edition (Issue 1) but looking at the valve clearance section and gap specification chart, at least that section is in the newer edition (Issue 2).

Gene


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