Bearcat chipper with Honda GX670

[PhillH]

Hi all,

 

Looking for some help with a Honda GX670 24HP engine.

 

The engine is down on power, to the point it stalls when engaging the fly wheel If you do not engage it really slowly (Flywheel spins freely so it’s not that.

 

I have checked the obvious such as plugs, valve clearance, fuel filter, cleaned the carb but still no different.

 

Has anyone had similar faults or have any ideas? It would be appreciated.

 

Thank you in advance.

[Wonky]

I'm not really sure if I can help.. but if I ask you 1 or 3 Questions, it may help you decide where to look next.

May sound silly,, Is the choke off ?  When you cleaned the carb did you clean the jet an the thing that airrates the fuel 

 

was the oil changed at regular intervals, and what intervals were they.  Oil can be good, but when it’s used by date comes by  ( oil change interval) it don’t work like it should.

did it use more oil ? Before you had the problem ? Does it burn oil, ie smoky on startup etc.  How old is the engine and how many hrs has it run approx 

A suggestion is low compression, and ring wear. 
 

check compression if low, I,d be looking at the ring end gap etc.

 

like I said engines wear a lot more when run too long on old oil as it don’t have its lubricant Quality like New or oil does. 
 

the spark plug colour tells a story as well..

 

 

 

 

[Wonky]

Engine governor working ok ..?

[Wonky]

I had a look around, found the 690 service manual, it should be pretty much the same, as you will see the models it covers. 😉

 

as I was looking through it, I,m not sure if you have one fitted , I know in the USA and other dry places they have to have a spark screen in the exhaust..if you have one and  it’s blocked  that will give low power.

 

heres the link to the service manual. 
https://www.lindec.com/download/14043667571_Honda_GX630-660-690-workshop_manual.pdf

 

and as you can see from the screenshot I took. Low power is because of some of the things I said before 👍

edit this  670 manual 

 

http://cdn.powerequipment.honda.com/engines/pdf/manuals/00X37Z6C6120.pdf

Edited May 1, 2021 by Wonky
Edit

[PhillH]

I had a look around, found the 690 service manual, it should be pretty much the same, as you will see the models it covers. [emoji6]
 
as I was looking through it, I,m not sure if you have one fitted , I know in the USA and other dry places they have to have a spark screen in the exhaust..if you have one and  it’s blocked  that will give low power.
 
heres the link to the service manual. 
https://www.lindec.com/download/14043667571_Honda_GX630-660-690-workshop_manual.pdf
 
and as you can see from the screenshot I took. Low power is because of some of the things I said before [emoji106]

edit this  670 manual 
 
http://cdn.powerequipment.honda.com/engines/pdf/manuals/00X37Z6C6120.pdf

Hi@wonky thank you for extensive reply, you have given me plenty to go at here. The issue I have is that I do not know the full history of the engine.

It’s starts fine hot and cold, there is no smoke and it does not use oil. The oil may not have been changed regularly enough as it does not get used a lot but totally understand what your saying. I am almost certain there is no spark screen but will check.

Next think to check is compression and governor.

I will report back, thank you.

[PhillH]

Hi all, finally got round to taking a look again today. Done a compression test on both cylinders wet and dry, both measured around the same and all reading’s are within the spec from the manual (85psi dry / 95psi wet)

I checked the temperature on each cylinder and it seems one side is not firing as it’s not getting warm, I pulled the lead and no difference but pulled the other side and it stalled.

With the plug out, it is sparking but it does seem to be slightly damp.

Has anyone had this issue before, next thing to check is if the coils are handed so I can swap them to try and rule out the coil.

Thank you in advance

[Paddy1000111]

2 hours ago, PhillH said:

Hi all, finally got round to taking a look again today. Done a compression test on both cylinders wet and dry, both measured around the same and all reading’s are within the spec from the manual (85psi dry / 95psi wet)

I checked the temperature on each cylinder and it seems one side is not firing as it’s not getting warm, I pulled the lead and no difference but pulled the other side and it stalled.

With the plug out, it is sparking but it does seem to be slightly damp.

Has anyone had this issue before, next thing to check is if the coils are handed so I can swap them to try and rule out the coil.

Thank you in advance

Probably a dumb question but have you stuck a new plug in it? Could be that the plugs a bit shite/not firing under compression. Other than that it could be the coil like you say 

[Wonky]

Yes, I agree with paddy. If you haven’t changed the plug for a new one, and are feeling tight or can’t get to the shop to buy a new one. Then swap the plugs around, and see if the problem is the same or now on the other side 🤔

 
Edit spark plugs sometimes  do odd things when under pressure or when they get hot.  I,m sure you can guess this checks two things by swapping the plugs around and is easy compared to swapping coils around.👍

Edited May 17, 2021 by Wonky
Edit

[Paddy1000111]

Also, just looked at the part numbers and they are sided. If you're good with spanners then just swap out both spark plugs with new ones and the fuel filter and try again as this is going to cost less than a tenner. If that doesn't work I would personally clean the carb, it sounds unlikely to be the issue but it's free to clean. If none of that works then I would buy a new coil

[Paddy1000111]

More specifically, part 30/31 on here. The high jets. I would take the bowl off, check it for garbage and then check those jets to see if one is blocked. Worth a shot for no outlay