GTI/Rfi No start in Water

[msmoak5]

Hey gang! So I’m having a helluva time with this 2005 GTI/RFI I have. I’m going to list everything I’ve done, replaced and/or trouble shot.

The top end was rebuilt with 1.0 over pistons. Prior to the rebuild, compression was showing 125 psi in both cylinders. After the rebuild, compression is only 135/134 both cylinders. Tried two different gauges and got the same results. Initially, the machine would crank and start on the water hose; however, would not start on the boat ramp. No codes are shown on my CANDOO. Ordered a replacement Rotary valve cover and it’s back to near perfect factory specs. I have checked every wire, ground and sensor. All are not showing any issues. Even replaced the exhaust hoses thinking there was a blockage….still nothing. Battery is new and charged and passed a load test. The impeller spins freely with no binding.

I am thinking the compression maybe causing an issue? I am considering purchasing new cylinder jugs with standard pistons and doing another top end build. Has anyone had any issues similar? The machine will fire up every time on the trailer and connected to the water hose, but literally will just crank on the ramp. I’ve even started it, back it down the ramp and it would run a few seconds and stop.

What am I missing?

 

[msmoak5]

Also fuel pressure is normal, fuel injectors are clear and spraying great. Getting bright spark at the plugs too.

 

[burtshaver2021]

Wow, that’s a tough one, you seem to have everything you need. I just posted to say 130/135 of compression is fine. It is low after a rebuild, I would expect 145 till the rings seat, then go a little higher. Not your issue but did you have the rave valves machined? Did you have the cylinders bored or just new rings and pistons? Did you adjust the oil pump lever so that it’s getting double oil for break in? Hopefully someone else comes on with a possible solution

 

[mikidymac]

Starting out of the water but not in is a good sign of low compression. Add that to only being 135 after a rebuild on two different gauges, something is wrong. Compression on a fresh engine should be very close to 150.

 

[msmoak5]

Wow, that’s a tough one, you seem to have everything you need. I just posted to say 130/135 of compression is fine. It is low after a rebuild, I would expect 145 till the rings seat, then go a little higher. Not your issue but did you have the rave valves machined? Did you have the cylinders bored or just new rings and pistons? Did you adjust the oil pump lever so that it’s getting double oil for break in? Hopefully someone else comes on with a possible solution

Hmm…didn’t have the cylinders bored, but did get new pistons and rings. I am thinking of getting all new jugs back to standard, with new standard pistons/ rings, but not sure if that’ll work? Or would I need to get 1.0 over jugs. I didn’t mess with the oil pump. Also didn’t do anything with the rave valves, but clean them and rebuild them.

 

[msmoak5]

Starting out of the water but not in is a good sign of low compression. Add that to only being 135 after a rebuild on two different gauges, something is wrong. Compression on a fresh engine should be very close to 150.

Thank you! I’ve seen your responses A LOT on this forum and I have a good deal a respect for you. I’m thinking of getting new jugs, pistons and rings, maybe going back to standard?

 

[burtshaver2021]

Hmm…didn’t have the cylinders bored, but did get new pistons and rings. I am thinking of getting all new jugs back to standard, with new standard pistons/ rings, but not sure if that’ll work? Or would I need to get 1.0 over jugs. I didn’t mess with the oil pump. Also didn’t do anything with the rave valves, but clean them and rebuild them.

I really don’t think compression is your issue, yes, 135 is not great but it’s well within range. Normally 120 is rebuild time. If you do decide to re sleeve and go back to standard piston size remember that you will need to have the new sleeves bored, they do not come ready to go. What size over are your pistons presently? .25mm is the only size over that machining of the rave valves is not required.

 

[msmoak5]

They were 1.0 over, so ended up putting the same size back in there, mainly because I thought I had a ring issue. I’ve even thought about going up to 1.5 over, but figured the sleeve would still need to be bored? When I bought this ski, the engine looked to be a SBT build. Not sure if it was a whole engine or just a top end from SBT. Also, is there a way determine if my race valves were machined for the pistons?

 

[burtshaver2021]

They were 1.0 over, so ended up putting the same size back in there, mainly because I thought I had a ring issue. I’ve even thought about going up to 1.5 over, but figured the sleeve would still need to be bored? When I bought this ski, the engine looked to be a SBT build. Not sure if it was a whole engine or just a top end from SBT. Also, is there a way determine if my race valves were machined for the pistons?

If you had it running then they have been machined,

 

[msmoak5]

It was. So in theory….if I were to get another full SBT top end kit, already set to 1.0 over, I shouldn’t have to do any thing with the raves other than maybe rebuilding the rubber pieces? Shouldn’t have to re-machine the valves?

 

[burtshaver2021]

It was. So in theory….if I were to get another full SBT top end kit, already set to 1.0 over, I shouldn’t have to do any thing with the raves other than maybe rebuilding the rubber pieces? Shouldn’t have to re-machine the valves?

That’s correct, but what do you mean by buy another 1mm over kit? Are you planning on buying some new cylinders and having them bored 1mm over? . See what @mikidymac says but in my opinion your compression is not your problem

 

[msmoak5]

Yes, I’m pretty much beyond frustrated. This has been my 4th ski to get and rebuild/ restore. What’s crazy was I decided to rebuild the top end because the compression starting dropping to around 125, so that’s why I did piston and rings, but I was expecting a higher reading after the new piston and rings. First RFI…which is a huge PITA! I’ve even purchased an eBay special ECM and it did the same thing, with the exception of that ECM had multiple codes popping up, so I figured that “newer” ECM was damaged. I could program a key, but it wouldn’t write it to the ECM. So I’ve gotten hung up on the compression. The one thing I haven’t done is check the spark while it’s sitting on the ramp…not sure if somehow it can be weaker with a load? Not sure if this makes a difference either, but when I got it, the rubber plug on top of the air box was missing. I’ve since replaced that plug, but not sure if it was removed to allow a little more air?

Sorry to bombard with so many questions, it’s been a pain with this one. I currently have it for sale, hoping someone else may want to figure it out, but if I could get it fixed, I’d keep it a while.

 

[mikidymac]

Ok, so it is a SBT engine which isn't a great start. They were boring everything that came in the door to 1.0 over and it isn't easy to find larger pistons than that so once they go they are either junk or you have to resleeve them.

Now, you had low compression 125 so you just installed new pistons and rings of the same size. That is going to probably be your issue as that will not bring compression back to the good range. You are seeing 135 now but it is going to continue to drop back to 125 or less because the cylinders are worn.

I would not install another set of SBT anything.

I would find a set of good clean cylinders and have them bored to the next oversize to clean them up and install new WSM pistons and rings.

 

[msmoak5]

Ok, so it is a SBT engine which isn't a great start. They were boring everything that came in the door to 1.0 over and it isn't easy to find larger pistons than that so once they go they are either junk or you have to resleeve them.

Now, you had low compression 125 so you just installed new pistons and rings of the same size. That is going to probably be your issue as that will not bring compression back to the good range. You are seeing 135 now but it is going to continue to drop back to 125 or less because the cylinders are worn.

I would not install another set of SBT anything.

I would find a set of good clean cylinders and have them bored to the next oversize to clean them up and install new WSM pistons and rings.

Awesome, thanks. So even installing used good cylinders with new standard piston and rings should be good too?

 

[mikidymac]

Awesome, thanks. So even installing used good cylinders with new standard piston and rings should be good too?

No, installing new pistons in any used cylinder is bad. You need to have them bored to the next oversize so the new pistons are in fresh, not worn out bores. They can be used cylinders but you have to have them machined by a shop that knows 2-strokes due to the ports.

 

[msmoak5]

So I probably wasn’t clear what I was thinking of doing….getting OEM standard cylinders, then having the cylinders resleeved with new sleeves bored to standard size with new standard pistons and rings. Or just re-sleeving my current ones with new sleeves bored to standard. Or would it be better to still just have my current sleeves bored up a size and new 1.5 over? Also is there a good shop to send them to? Not sure of any in my location. I’m in Pawleys Island, south of Myrtle Beach, SC.

 

[burtshaver2021]

There’s no benefit to buying new cylinders and resleeving them, then boring to standard size. If you’re going to re sleeve some cylinders you might as well just resleeve the ones you have. I think sleeves are about 75.00 a piece. Then the bore is about 100.00 per hole. Or option 2 is to buy a used set of cylinders and just have them bored out to the next size, so if they are standard size, have them bored .25mm or .5mm over size, really up to your machine shop after they measure them for out of round, taper.. the only problem is you will have no way of knowing for sure what size they are

 

[DaddyLoafin]

I've seen people on the Facebook group who do cylinder exchange but i wouldn't be able to tell you what their names are. The one guy even would post pictures of the ports so you can see the chamfers on them.

 

[msmoak5]

Makes sense. May just start with my current ones and bore them to 1.5 over. I’ll keep y’all posted on what I decide.

 

[mikidymac]

I would stay away from the 1.50 over as the sleeves are getting really thin. The only place that sells 1.50 over is SBT and I don't need to tell you the quality of SBT parts.

Have your cylinders re-sleeved and go with STD sized pistons and rings. If you get clean used cylinders just have them bored to the next size required to clean them up, no reason to have them re-sleeved.

 

[msmoak5]

I would stay away from the 1.50 over as the sleeves are getting really thin. The only place that sells 1.50 over is SBT and I don't need to tell you the quality of SBT parts.

Have your cylinders re-sleeved and go with STD sized pistons and rings. If you get clean used cylinders just have them bored to the next size required to clean them up, no reason to have them re-sleeved.

Sounds like a plan! Thanks!