Yesterday's Tractor Co. Parts for Farm Tractors - Compare our Prices!
Click Here or call 800-853-2651 
   Allis Chalmers Case Farmall IH Ford 9N,2N,8N Ford
   Ferguson John Deere Massey Ferguson Minn. Moline Oliver
 FAQFAQ   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   Traditional YT Forum ViewClassic View   RegisterRegister 
 ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in 

GX390?


 
Post new topic    
View previous topic :: View next topic  
Author Message
George Marsh
Tractor Guru


Joined: 05 Aug 2009
Posts: 6064
Location: terre haute

Report to Moderator

PostPosted: Mon Oct 15, 2012 4:51 pm    Post subject: GX390? Reply to specific post Reply with quote

I have a Honda GX390 on a 3700 psi pressure washer. I'm getting hard to start after it's set for a few months and I'm not getting any younger. Once I get it started, it's easy to restart. I crank the water pressure adjust to minimum and pull the trigger on the wand to remover load from pump.

Just wondering if perhaps the valves aren't set right? I've read one place the intakes are .02-.04 and exhausts are .08-.010. Does this sound right?

Also read the engine has auto decompression that operates off the exhaust valve. So if the exhausts are not on the money, could this be why it's hard to start?

Engine has a low oil pressure switch. Is it possible that I don't have enough poop to get the motor turning fast enough to build oil pressure? Once the oil is warm, it's easier to start. Should I try a thinner oil? What grade?

Does anyone have a flywheel with starter teeth and a starter? Love to have electric starter.

Does anyone have other ideas I could try?

Seriously thinking of buying a new pressure washer with electric start.

There are about 4 different pumps on the market. What's your favorite?

George
 
Back to top
View user's profile
RGMartin
Tractor Expert


Joined: 14 Jan 2011
Posts: 2210


Report to Moderator

PostPosted: Tue Oct 16, 2012 3:32 am    Post subject: Re: GX390? Reply to specific post Reply with quote

George Marsh wrote:
(quoted from post at 20:51:15 10/15/12)
Engine has a low oil pressure switch. Is it possible that I don't have enough poop to get the motor turning fast enough to build oil pressure? Once the oil is warm, it's easier to start. Should I try a thinner oil? What grade?



The low oil switch is a Oil level sensor, not pressure. If that is the issue, rocking side to side will usually get it going. You could also try bypassing the switch if you keep an eye on your oil level.


390s are a big engine to pull by hand.
 
Back to top
View user's profile
George Marsh
Tractor Guru


Joined: 05 Aug 2009
Posts: 6064
Location: terre haute

Report to Moderator

PostPosted: Tue Oct 16, 2012 3:47 am    Post subject: Re: GX390? Reply to specific post Reply with quote

RGMartin,
For some reason, I thought the sensor measured oil pressure. I have a 20 hp kohler that I'm sure it's sensor measures pressure, because every time I change oil and filter, it takes a few more cranks before the engine makes a spark. Once I goofed, pulled the choke to start the enging after changing oil, About 10 cranks later the spark arrived and shot fire out the muffler. One BIG BANG.

Because the 390 doesn't have an oil filter, you may be right. What tells the sensor there is the presence of oil if it doesn't use pressure?

You're right, it takes a lot to crank a 390. My right arm is still hurting.
George
 
Back to top
View user's profile
Billy Shafer
Tractor Expert


Joined: 24 Apr 2009
Posts: 3176


Report to Moderator

PostPosted: Tue Oct 16, 2012 6:50 am    Post subject: Re: GX390? Reply to specific post Reply with quote

The 390 has a splash lube system. No oil pump so no pressure. The level switch is the only oil protection it has. The Honda switch is more reliable than most.You can unplug it and see if it makes starting any better.But I don't think that is your problem.

How many hours on the engine,is compression good, valves set properly.

If you are like me. The main problem is age. Ain't as young as we used to be.
 
Back to top
View user's profile
Billy Shafer
Tractor Expert


Joined: 24 Apr 2009
Posts: 3176


Report to Moderator

PostPosted: Tue Oct 16, 2012 6:57 am    Post subject: Re: GX390? Reply to specific post Reply with quote

Almost forgot. Valves

Intake 0.15 MM
Exhaust 0.20 MM
 
Back to top
View user's profile
George Marsh
Tractor Guru


Joined: 05 Aug 2009
Posts: 6064
Location: terre haute

Report to Moderator

PostPosted: Tue Oct 16, 2012 9:09 am    Post subject: Re: GX390? Reply to specific post Reply with quote

Billy, thanks for the info.

Bought pressure washer used. It has no hour meter. As for compression, YES, that's what makes so hard to start. Sometimes it fires too early and pulls the starter out of my hand.

Going to check valve clearance and put a thinner oil in it.

George
 
Back to top
View user's profile
George Marsh
Tractor Guru


Joined: 05 Aug 2009
Posts: 6064
Location: terre haute

Report to Moderator

PostPosted: Tue Oct 16, 2012 1:30 pm    Post subject: Re: GX390? Reply to specific post Reply with quote

Billy,
Checked valve clearance. Both were close. Tightened the exhaust perhaps .001-.002 inches. Nothing major. However, I did notice what Honda called using the exhaust valve as a decompression valve. When I rolled the motor over slowly, the intake valve open and closed. On the compression stroke, the exhaust valve opened a small amount and just breifly. Then on the exhaust stroke, the exhaust valve opened even more and stayed open for a longer time.

How does Honda do this? I'm guessing it has 2 lobs on the exhaust cam. Or is there another way to get the exhaust valve to open briefly on the compression stroke just while you are starting the engine? Wouldn't this send a small amount of fuel/air mix out the exhaust before there is a spark?

Do other small engines do the same thing making it very critical to keep the exhaust valve clearance spot on the money?

Thanks,
George
 
Back to top
View user's profile
Billy Shafer
Tractor Expert


Joined: 24 Apr 2009
Posts: 3176


Report to Moderator

PostPosted: Tue Oct 16, 2012 2:21 pm    Post subject: Re: GX390? Reply to specific post Reply with quote

George. Those are cold settings. The cam lobe controls compression release. No other way that I know of. Briggs has the same system.I should have the 390 manual somewhere around my nice clean office.I will check.
 
Back to top
View user's profile
George Marsh
Tractor Guru


Joined: 05 Aug 2009
Posts: 6064
Location: terre haute

Report to Moderator

PostPosted: Tue Oct 16, 2012 6:36 pm    Post subject: Re: GX390? Reply to specific post Reply with quote

Billy,
I adjusted the valves when cold. Exhaust was only about .002 in out. I did notice the exhaust valve opening a little on the compression stroke? Does the cam do that? Are there 2 lobs on the cam?
George
 
Back to top
View user's profile
JDseller
Tractor Guru


Joined: 09 Jul 2010
Posts: 4484
Location: North-East Iowa

Report to Moderator

PostPosted: Wed Oct 17, 2012 2:33 am    Post subject: Re: GX390? Reply to specific post Reply with quote

The cam has a weight that is on a lever. That lever turns a small shaft that has an eccentric on the end of it. That eccentric sticks out into the exhaust lobe of the crankshaft. The weight it held one way with a spring. So at low speeds the eccentric will open the exhaust valve a little at crank speeds. When the engine hits and comes up to running speed the weight over comes the spring pressure. Then the eccentric is flush with the cam lobe and no longer hits the exhaust valve.

Have you tried a new spark plug. I have a JD pressure washer that has a Honda motor on it. If it starts hard it usually is the spark plug not firing right under compression. Also are you able to crank it good and fast??? As my Dad has gotten older he can't pull the rope fast enought for small engines to start correctly. He complains about this one or that one not starting correctly. Me or my sons can just give it a good yank and the engine starts fine.

I have actually mounted a few snow blower motors on some of the things he uses with a small gas engine on them. The snow blower motors have 110 volt electric start on them. So he can just plug in the cord and hit the button and away he goes.

One of his motors was the same model as one used on snow blowers. I was able to change the flywheel to one that would use the electric starter.
 
Back to top
View user's profile
Cienna
Regular


Joined: 22 Nov 2010
Posts: 156


Report to Moderator

PostPosted: Wed Oct 17, 2012 3:19 am    Post subject: Re: GX390? Reply to specific post Reply with quote

George----I have an 8hp pressure washer---about the same as your GX390. I have the same issue with it. What makes it hard to pull is that you're pulling against water pressure. What I do is lay the wand down on the ground with something to hold the trigger open. Makes a lot of difference. Also use a leather glove to pull the rope. (Redneck solution!!)
 
Back to top
View user's profile
George Marsh
Tractor Guru


Joined: 05 Aug 2009
Posts: 6064
Location: terre haute

Report to Moderator

PostPosted: Wed Oct 17, 2012 3:35 am    Post subject: Re: GX390? Reply to specific post Reply with quote

JDseller,
I'm looking for a flywheel and starter. I think my problem is I'm getting old. 3 days later my arm and sholder is still hurting from pulling on the starter.

May buy myself a new pressure washer with a starter for Christmas.

My 6.5 briggs on a pressure washer is a dream to start, but the gismo that adds soap and bleach is broken. It's built into the pump. I would have to buy a new pump to fix the problem. I need to do something, still have 3 properties to clean.

George
 
Back to top
View user's profile
Chip812
Long Time User


Joined: 20 Aug 2011
Posts: 778
Location: ALABAMA

Report to Moderator

PostPosted: Wed Oct 17, 2012 6:30 am    Post subject: Re: GX390? Reply to specific post Reply with quote

It could only be that the carburetor is starting to get gummed up due to intermittent use. I would try a fuel additive/stabilizer. I prefer Seafoam, but there are others that are just as good on the market. I tend to also get the ether out and give it a shot or two so that it starts on the first pull.
 
Back to top
View user's profile
Display posts from previous:   
Post new topic    Yesterday's Tractors Forum Index -> Tool Talk All times are GMT - 8 Hours
Page 1 of 1

 
Jump to:  
TRACTOR   PARTS TRACTOR   MANUALS
Same-Day Shipping! Most of our stocked parts ship the same day you order (M-F).  Expedited shipping available, just call!  Most prices for parts and manuals are below our competitors.  Compare our super low shipping rates!  We have the parts you need to repair your tractor.  We are a Company you can trust and have generous return policies!   Shop Online Today or call our friendly sales staff toll free (800) 853-2651.

YT Home  |  Forums Home

Copyright © 1997-2014 Yesterday's Tractor Co.

Powered by phpBB © 2001, 2005 phpBB Group

All Rights Reserved. Reproduction of any part of this website, including design and content, without written permission is strictly prohibited. Trade Marks and Trade Names contained and used in this Website are those of others, and are used in this Website in a descriptive sense to refer to the products of others. Use of this Web site constitutes acceptance of our User Agreement and Privacy Policy

TRADEMARK DISCLAIMER: Tradenames and Trademarks referred to within Yesterday's Tractor Co. products and within the Yesterday's Tractor Co. websites are the property of their respective trademark holders. None of these trademark holders are affiliated with Yesterday's Tractor Co., our products, or our website nor are we sponsored by them. John Deere and its logos are the registered trademarks of the John Deere Corporation. Agco, Agco Allis, White, Massey Ferguson and their logos are the registered trademarks of AGCO Corporation. Case, Case-IH, Farmall, International Harvester, New Holland and their logos are registered trademarks of CNH Global N.V.

Yesterday's Tractors - Antique Tractor Headquarters