FD620D to FD661D

[JohnF]

Researching my engine a bit I ran into some interesting things. At a tractor racing club site a guy that knows Kawasaki engines (jaysonmikula) said the following:

When the number ends in zero (0), it represents rough displacement in cc's. The numbers ending in one (1) are either a down or up hp tuning of the base engine in its family.

Really? I've been reading through the FD620D/FD661D service manual. The FD620D is rated 20HP and the FD661D is rated 22HP. What is the difference?

Carburetor jetting. That's it. That's all I can find so far. I checked camshaft and valve part numbers - same. Everything except the jetting looks to be the same.
Okay, there are some other differences. Starter looks to be different. FD661D has a higher low idle. The FD661D has a shutoff relay. But nothing I can imagine that would affect HP.

So, from the service manual:

FD620D-FD661D jetting.jpgFD620D-FD661D Alt Jetting.jpg

It looks like an easy and inexpensive 10% HP increase. If anyone tries this I would suggest watching the spark plugs closely for signs of running too lean at least for awhile.

If anyone finds a difference that makes this a bad idea then post it here.

Kawasaki Engines 16035-2068 - JET-AIR,#1.4
Kawasaki Engines 16035-2069 - JET-AIR,#0.8
Kawasaki Engines 92063-2222 - JET-MAIN,#106
Kawasaki Engines 92063-2219 - JET-MAIN,#108
Kawasaki Engines 92063-2239 - JET-MAIN,#110

I already have the #110 and #108 main jets. Right now at tewarehouse.com this upgrade would cost me $28 and 1/3 of that is shipping.

[NOTE]

Read further! I also found that you will need a different piston and a different spark plug.

[Rock Doctor]

I'm in

I will try to order parts today

RD

[Rock Doctor]

Hmmmm
It would seem that they don't ship to Canada
Anyone willing to buy the parts and ship them to me? I will pay you back, you can trust me

Kawasaki Engines 16035-2068 - JET-AIR,#1.4
Kawasaki Engines 16035-2069 - JET-AIR,#0.8
Kawasaki Engines 92063-2239 - JET-MAIN,#110




RD

[trevorakm1]

just sent you a message RD.

[trevorakm1]

RD not a problem just figured safer to get correct parts if you order and send to my address and I foward them to you. you got the address feel free. by the way you mailbox is full.

[Rock Doctor]

RD not a problem just figured safer to get correct parts if you order and send to my address and I foward them to you. you got the address feel free. by the way you mailbox is full.

You are the Man
Tks

I just sent an email to the place I bought my 27hp Kawi from, if they can't help me I will get back to ya

RD


EDIT
Apologies for the Hijack, we can get back on track now

Hmmm, that's very interesting. Thanks for pointing this out John, I'm interested in looking into this further..

[JohnF]

Tracked down the piston part numbers - they differ. May be a bit different compression ratio.

FD620D piston is 13001-2186
FD661D piston is 13001-2196

These look to be $30 a piece.

rings and piston pin are the same.

FD620D compression ratio is 9.0:1
Haven't found compression ratio for FD661D

Found an old flyer in PDF format that I tried to link but it's too big.

FD661D compression ration is 10.3:1 and spark plug is BMR6A

So dang, it's not just jetting. But pistons aren't hard if you have your engine out anyway.

Ignition is the same.

[gimmegreens336]

Still though, only jets pistons and plugs? That's crazy... good research, keep it coming

[gimmegreens336]

If anyone tries this I would suggest watching the spark plugs closely for signs of running too lean at least for awhile.

Just for the sake of learning, what type of things show on the spark plugs while running lean?

[JohnF]

Just for the sake of learning, what type of things show on the spark plugs while running lean?

No learning for you.
Come back, ... one year.

I actually would expect with the jetting changes that it would run rich. Mentioning that a person should watch for lean condition is mostly CMA. (self directed CYA)
Running lean can destroy an engine. Running rich probably won't.


Do a search for reading spark plugs. Basically, you are looking for signs that the engine is running really hot. Hot enough with too much oxygen and metal can burn.
Anyway, whitish residue all the way up to melted electrodes.

[gimmegreens336]

I melted an electrode slap off at Busco! Some of those fellas saw it - lewis, fmints, 6x6, dan67, etc... I bet it was from a gummy carb not allowing enough fuel to the motor? Crazy... I love this stuff

[AlbertaRider]

Tracked down the piston part numbers - they differ. May be a bit different compression ratio.

FD620D piston is 13001-2186
FD661D piston is 13001-2196

These look to be $30 a piece.

rings and piston pin are the same.

FD620D compression ratio is 9.0:1
Haven't found compression ratio for FD661D

Found an old flyer in PDF format that I tried to link but it's too big.

FD661D compression ration is 10.3:1 and spark plug is BMR6A

So dang, it's not just jetting. But pistons aren't hard if you have your engine out anyway.

Ignition is the same.

So the piston for the FD661D would be slightly "taller"(from wrist pin to top of piston) than the FD660D creating the increased compression ratio? Or is it the shape of the top of the piston that is different?

[JohnF]

So the piston for the FD661D would be slightly "taller"(from wrist pin to top of piston) than the FD660D creating the increased compression ratio? Or is it the shape of the top of the piston that is different?

That is one way it is done. Sometimes low compression pistons are slightly dished or high compression pistons are slightly crowned. I don't really know how these are done because I can't find this kind of specific dimension of any of the parts. I am getting my information from a comparison of parts lists and then cross referencing with the Service Manual Supplement for the FD661D. Dimensions given are only for parts that have a service limit or must meet some install dimension and the difference in these pistons is not mentioned anywhere I have found.

I don't know if I mentioned this (I will check the original post) but I see that the FD661 has a different spark plug: BMR6A. It is probably a bit shorter.

[AlbertaRider]

That is one way it is done. Sometimes low compression pistons are slightly dished or high compression pistons are slightly crowned. I don't really know how these are done because I can't find this kind of specific dimension of any of the parts. I am getting my information from a comparison of parts lists and then cross referencing with the Service Manual Supplement for the FD661D. Dimensions given are only for parts that have a service limit or must meet some install dimension and the difference in these pistons is not mentioned anywhere I have found.

I don't know if I mentioned this (I will check the original post) but I see that the FD661 has a different spark plug: BMR6A. It is probably a bit shorter.

Sounds like a rather simple way to get a couple of HP out of my engine, I'd like to get back the HP the alternator steals from mine. I had a ground wire come loose off the alternator circuit and I could feel the HP increase as soon as it happened. That little bit of gain really made a difference in manouvering in the muskeg while loaded (not me, the ARGO.lol) I plan on splitting the shell and taking out the motor and tranny to "tweak" the engine and rebuild the tranny so this type of engine mod would be ideal at that time. Will look into fitment and availability of parts for this neck of the woods. Thanks for the tip!

[JohnF]

I am on a similar path. (Plan on making a thread about it soon!) You don't need to split the shell to take the powerpack out. Argo Service Manual section EN (Engine System) has the detail of removing the powerpack. Here's one from beaverdamargo.com.