Little help from the engine guys (20hp Kawi)

[Rock Doctor]

OK, I am no Small Engine Mech, but I might be well on my way to justifying a new 29hp for my Conquest 2004.

Symptoms:
Smoking a bit when started
Seems to be loosing power when it gets hot
Knocking when under load (Stops knocking when more throttle applied, sometimes) This is what buggs me the most.
Almost 700 hrs on engine
Engine seems to be getting hotter than normal , on trips that I've made plenty of times before.

Clutches are new and in good condition.
Belt is good
Trans is fine and not dragging.

I was told to set the valves to .001" clearance, is this correct?
I can do a compression test, but what press should it be?
Could "Timing" be the problem? How is it checked/set?

Yes, I could go to my local Argo Dealer and ask them, but I believe I would be just as well off asking my dog.

Any idea would be appreciated


RD


I have the OK from the "Pettycoat Gov't" to go ahead and order the new engine, but would also like to make sure this one is in good condition before I pull it out.

[Roger S]

I googled fd620 and got .010 for valve clearance

a puff of blue smoke on morning starts is valve seals. Otherwise it's just accidental upper cylinder lubrication.

One guy said 165 on compression. (won't have that much if the valves are at .001)

some 620's are prone to cam lobe wear, if the valve lash is very loose and the adjusting lock nut is still tight, might indicate this condition.

Isn't there a belt that drives the engine cooling fan?

[Rock Doctor]

Tks Roger, I never even thought of googling the clearance thing. .001 sounded tight to me.

One guy said 165 on compression. (won't have that much if the valves are at .001)
Do you think you could explain this to me?
Valves are not at .001, I wanted a little clairification first.

The belt appears to be tight and in good condition, but I think I just might replace it to be sure.

Any thoughts on the "Knocking"/"Rattle" coming from the engine when it's lugging a bit (Lifters/Tappets)? I realize that if I lug the engine, it will do that, but it seems to be much worse now than it used to be.

RD

[Roger S]

Smaller intake valve clearance will close the intake valve later, that's when compression starts..

I didn't comment on the other stuff, since I've hardly had the hood open on the conquests.

The pucks in my drive clutch rattle a lot at idle.. sounds like engine noise. Can't tell from here.. the way you describe.. goes away under more power. Cold knock is sometimes piston clearance.

[Pophamrt1]

Roger covered most of it, but some added info…

Minimum acceptable compression is 170PSI. The engine should be warm, the plugs out, and the carb throttle and choke held open with gas disconnected/pinched off. Turn it 6-7 times until it stops pumping up. Make sure the battery is strong/on a charger as sometimes you’ll get uneven readings as it wears down. I have 200/205 PSI on a 300 hour Fd620, which may be a bit high (suggests almost 10:1 compression, carbon, etc. could be built up). If the compression is low, add a squirt of motor oil. If it comes up, it’s the rings that are worn. If not, it’s the valves not seating/burned (or both).

Intake/Exhaust valve clearance is 0.01” (0.25mm) NOT 0.001” Be careful, running that tight will burn the valves pretty quickly. Smoke on startup is fine. As Roger said, its just valve guides wearing a bit.

The engine temp should stay around 185F, and not exceed 225F. It can go anywhere in between safely. Engines typically don’t run hotter: Cooling systems decrease their capacity. If its spiking under load, the capacity of the cooling system is likely down due to belt, thermostadt, pump or radiator wear. The thermostadt can and often does create a restriction. It needs to start opening at about 150F and to be at 0.28” minimum lift by 175F. If it drags, or partially opens you get diminished cooling like described. Take it out and test it. Make sure the radiator cap is sealing too—it’ll drop your cooling efficiency the same way. Belt tension should be checked. Radiators are usually fine, but if it looks muddy, it won’t transfer the heat away. A bad bearing can cause added heat though.

Knocking at low rpm, on startup, and under load is likely a worn connecting rod bearing. Under load it can be a main bearing. However, you would normally notice an accompanying drop in oil pressure from the added clearance. Minimum operating pressure should be 40PSI at 3600rpm, and the oil pressure LOW detect switch kicks in at about 14PSI, at just off idle. A bearing issue can cause added heat from added friction too. Generally though, bearings are gradual wear, cold noises that go away when warmed up, re-appear under load, and get progressively worse with use. If it is the problem it’ll seize though, so watch the remote trips.

Hope this helps.

[Rock Doctor]

Helps??

More than helps, you guys are awesome, Tks

I should be able to look into most of this in the next few days. I also hope to have some HDI Bearing Assemblies to install on my Conquest (We'll see how that works out).

About the last thing of interest right now is that the Canadian and USA Kawi Distributers both say they don't have a 29hp DFI Kawi in stock, and that I will have to order right from Japan. Gad, I hate it when a plan doesn't come togeather.


Thanks Again Guys
If there are any other suggestions out there, I'm all ears, lol

RD

[Pophamrt1]

You're welcome... your posts are really helpful and we've all benefited. We have to keep you going!

Just a thought on the replacement engine. The 29hp Fd791D is a good choice, but the FD750 has some advantages. Fuel injection is great, but may not be the best choice for someome who needs to fix the rig in the middle of the bush. If I was running it, I'd bring a spare computer, injector, high pressure pump, 02 sensor, and a handful of misc. sensors. The FDs EFI systems have a solid reputation but, unlike a carburetor, when they go south there's no work around. With a carb you can usually rig something to get pressure and delivery. EFI you're done. The exception being the benefit of the EFI at high altitudes or extreme colds where its likely worth the trade off.

The other issue is modifications. You can tweak the FD750 from 27 hp to well over the 29hp efi version. Likely up near 37HP just by making it breath and rev. While the FD750 can be de-governored, rev kit added, intake opened up, and exhaust modified, the EFi 791 is stuck where it is. The FD750's carb can be adjusted, but the FD791's fuel curve can't be modified until someone starts remapping the EFI units fuel/Ignition curves and burning new profiles.

The only physical difference between the two engines out of the box is a slighly higher compression ratio. Same block, valves, etc. Just something to consider.

[Rock Doctor]

Good points, I am looking into that now. I'm not so much concerned with Altitude changes, but the cold winter starts can be a bugger with the carb.
Sending a note tpo the supplier now to check availability.

[Rock Doctor]

OK, so I set the Valves and did a compression test (Vids in progress), and I also fixed the heat shield around the exhaust (Knocking noise has mysteriously vanished..........Damn loose heatshield, lol)
Engine is running Awesome, purring like a kitten......................(Don't tell the wife, 'couse I already ordered a new engine 27hp)

I got 180PSI on my front Cylinder and only 160PSI on my rear Cylinder. I squirted about a Teaspoon of oil into the rear cylinder and tested it again, it got up to about 174PSI with the oil, so I'm assuming that I might have damaged rings on that cylinder, or I guess it could be a valve seat problem. It's not to bad yet though so I won't worry about it.

Tks Guys
RD

[Roger S]

LOL, the mystery engine knock is fixed.