2001 GTX-RFi (200-250 hours) head rebuild?

[rogierbanis]

Hi Forum,

Many many times i have read in this forum that around 200-250 hours on a 787 GTX-RFi you need to have the head rebuild and around 300hrs the cranckshaft. Now i was wondering is this interval based on experience or prescribed by the manufacturer? I can not see this in the shop manual. Reason i ask is that i have this type of engine and 225 hours on it. It still runs great and has specified topspeed but is getting a little more issues starting on the water which makes me think about compression.

Who can enlighten me on this. My dealer says that there is no manufacturer specification regarding the head rebuild.

Thank you all.

Best regards,
Rogier - Netherlands

 

[mikidymac]

It would be a top end rebuild and not the head.

But to answer your question there is no set time to rebuild. The 250 hours is just a general statement. If your compression is still around 150-130 psi. It’s still good and keep riding it.

As far as the crank, with about 300 hours they will typically not survive a new top end but that doesn’t mean you have to replace them at 300 hours if it is running fine.

 

[rogierbanis]

Thanks Mac.
What is the difference then between a top-end rebuild and a head rebuild?

 

[mikidymac]

There is no such thing as a "head rebuild" on these skis. The head is just a piece of solid aluminum, not like a 4 stroke head that has cams and valves in it.

A top end rebuild is replacing the pistons, rings, upper connecting rod bearing and piston pin and typically having the cylinders bored.

 

[rogierbanis]

Thanks!!...Again something learned.
Awesome forum this is...:cheers:

 

[rogierbanis]

Yesterday i performed a compressiontest and on both the PTO as the MAG cylinders i read a 130PSI average on 5 tests per cylinder. I have performed the test with both plugs out and full throttle. Seems OK to me then. What i did notice is that both sparkplugs where black-ish. I have no idea how old these plugs are since i own this Doo for 12 weeks now. It runs great by the way only some difficulties starting when in water. With my freshly received Candoo i figured out that the TPS is 4.3% opened when idle so i will adjust that first and re-test starting in water. Further no active errors show up in Candoo only 2 occasions of fuelinjector to ground on both injectors occured.

What do you guys think about the black plugs?

Thnx

 

[mikidymac]

It is a 2 stroke so it burns oil with the fuel. Black plugs are an indication that it is getting enough oil to protect the engine parts. As long as it isn't fouling them and not starting it is fine. You are much better off with a rich 2 stroke than a lean one.

So, it's perfectly normal.

 

[rogierbanis]

Ok great, Thanks. I will keep an eye on the plugs in the new season with new plugs installed. What is your opinion on the 130psi? I can’t seem to find the best pressure value here although 130 to me sounds perfectly fine.

 

[mikidymac]

150 is perfect 120 is time for a rebuild. Often times gauges are off so as long as both cylinders are even and it is running good I wouldn’t worry about it too much.

 

[rogierbanis]

150 is perfect 120 is time for a rebuild. Often times gauges are off so as long as both cylinders are even and it is running good I wouldn’t worry about it too much.

Ok thanks for the clarification. I think all will be good then. Both cylinders exact the same reading and engine runs great besides from the hard starting but i guess that will be fixed with the TPS reset and recalibration. It now runs 1400RPM on the trailer and that should be around 3000 from what i've heard.

 

[mikidymac]

Correct RPM is 3,000 on the trailer and 1,400 in the water. Honestly I am not sure how you adjust it on the RFI skis.

 

[PGHMAN]

The RFI has a throttle body is where the idle is adjusted. I'll pull a pic and post.