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Honda GCV 135 OHV 4.5hp engine starts when cold but then stops?

Honda GCV 135 OHV 4.5hp starts when cold but then stops
Engine will only restart easily when cold. Starts on choke, then I switch almost immediately to unchoked for about 10 seconds before the mower cuts out. Will not start again on choke or unchocked till the engine is cold.
No apparent carbureter or fuel problems. Any ideas?

Simon Clark, May 2008

home Fix label Garden Tools label_important Lawn Mowers category Hondadone

This was on a GC135 but this forum solved my problem. Engine was hard to start and would die after running 15 - 30 seconds. Checked gas flow from tank. Okay. Seemed like maybe the fuel pump. Replaced it. Same problem. Replaced carburetor. Same problem. Read this forum. Topped off oil level. Same problem. Replaced spark plug. Last thing I thought would be the problem. Runs like new! The wide gap on the old plug or the carbon buildup must have been overloading the ignition system somehow. Recommendation... Before tearing everything apart or replacing anything, change the spark plug.

Kateech, August 2020

Just fixed mine with a new £3.99 spark plug. Started and ran perfectly first time! I tried a first start after winter lay off 2 days ago. It eventually started but ran very fast for about a minute then cut out. I did the air filter and the carb stuff but still the same. It started first time after removing old spark plug and cleaning it but immediately reverted to cutting out. Last season it would only run on choke and also hunted and spluttered. Best £3.99 I ever spent!

dorsetapplecake, February 2013

One further thought: the general-purpose mower spark plug as sold by B&Q is not suitable for Honda mowers. The manufacturer`s specified part is essential for efficient combustion.

Pedro, May 2012

When this problem occurred, I thought there must be a timing fault, but a new plug NGK BPR 6ES has completely cured it (£4.78 including p&p). Thanks to those who offered advice. The mower is as good as new again.

Pedro, May 2012

As the mower had not been used since last summer I striped and clean the fuel tank, carb and lines.
Replaced the spark plug.
However when the engine runs it continues hunting and is very hard to start.
I have striped the carb again thinking it was the main jet but I still have the problem
I may have to concede and take it in for repair.

Dom, April 2011

Fitted a new NGK BPR6ES spark plug today and the mower is now running like a dream.....Thanks .

mainwaring, August 2010

I have the same problem with my mower it starts fine when cold but cuts out after a few minutes.I have cleaned the carb but it`s still the same, I am going to try fitting a new spark plug tomorrow .

mainwaring, August 2010

I had similar problems, and also engine speed was constantly varying when running warn. When I added choke, then the engine speed was OK.

I removed the carburetor, and noticed that the main jet was loosened. The I cleaned the carburetor and fastened the main jet, and the engine worked fine after that !

Harska, June 2010

i had a similar problem. i was advised to change the sparkplug . now runs great
recomended plug is a gkn bpr6es (which i bought from ebay £2.50+ postage tried all the garden centres they had none
when you get new plug the gap should be between
0.028 to 0.031 a cheap set of feeler gauge from halfords would do.if not google HONDA GCV135 i found a good manual for this engine

kenny c., May 2010

Hi, just to say I had a problem with a honda engine on a mixer. changed carb, plug put original carb back, turned out to be low of engine oil, did'nt realise but written on the starter housing was a warning to tell you. worked for me, good luck.

steve martin, May 2010

Exact same problem, did all the above (spark plug, fuel, carb cleaning session... ). Turned out to be the air filter. Try removing the air filter and start it up. Get a new filter, or use pressurised air to clean it (from inside out).

Anders, May 2010

the rpm does not remain stable and engine revs up and then slows down. Is it a problem with the carb or the governor

Cahn, August 2009

Thanks Marty - had the same symptoms and followed your advice, cleaned the spark plug, drained the fuel tank plus drained the carb float chamber. Filled with fresh unleaded and engine running fine now. Saved a small fortune by not having to take to the garage!

Andy, April 2009

were all guilty of not servicing mowers, but this engine is good ebay £5 for plug and air filter try this first, ive looked at these carbs after 7 years still like new so dont get carried away and start stripping it down! if the plug is shot it appears to sound like a compression leak,dont ask me why new fuel is also a good move

marty, March 2009

Same problem. I cleaned the spark plug (rather sooty) then syphoned out old fuel and added freshly bought unleaded. I started it on full choke and kept varying between choked and unchoked not letting it die. It eventually kicked in and ran properly, thank goodness. It's always been very critical on this engine getting the choke just right for starting and then making sure that when the engine starts to fully run that you adjust it so that there is no choke. Practice moving the throttle lever up and down and look at the engine to see when the choke is engaged and dis-engaged. It should then run perfectly.

Chris, February 2009

I could start mine, but then engine goes unstable after just few minutes and stalls. After that almost not possible to start. Had the engine checked and carb cleaned by the dealer - didn't help. Was then advised NOT TO OVERTIGHTED the fuel cap!!! It did help actually! The rubber pad in the cap has some grooves that can be blocked once closed very tight.

Alex, June 2008

I had this problem with a generator, it began when I topped up the petrol. After much cleaning of the carb I got it to run as long as I kept it half choked. It finally turned out that I had used old unleaded petrol - about 6 months in the can. After filling with new fuel and a few false starts it runs perfectly.

Alan Mudd, June 2008

Mine started to behave like this, usually showing signs of a weak mixture.... coughs & splutters, backfiring. Cleaned the carb thoroughly (using an airline for the jets), which made little difference. Changed the plug, and it's much better... have you tried a new plug yet?

highrange, May 2008

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