sam111

Hey Guys,

Ive got a vx cruiser. The problem ive got it is : when i apply full throttle, its not getting full revs which isnt allowing to get top speed. ive changed my plugs, oil, oil filter, check my air filter. The first ride after this service, it ran fine with out any problems. i took it out today, and the problem started again. My coils look to be stuffed, could that be the issue?

Help would be highly appriciated...

Ernest T

Not saying you couldn't have a bad coil, but its a fairly rare problem. I'd pull the plugs again after you have run it, and look for the wet one. These plugs foul very easily, and I'd change out the plugs as a first step for any performance decrease on this model engine. At least change out the wet plug first.........new plugs solve about 90% of any performance problem on the MR-1 engine. Be sure the plug gap is correct.

Still have a problem after the above, then with the plugs out check for spark on each. If no spark on one then replace that coil (watch for gas blowing out of the holes when you do this = cover with a rag). The coils are not cheap (over $100 each).

Other things to look at: be sure the ski is not overfilled with oil. I've seen the exact symptoms when there is too much oil, which is an easy mistake to make on this model ski (got to check it when the engine is HOT). If you have good spark on all cylinders, the next most likely problem would be a dirty fuel injector.

__________________
2008 Yamaha FX HO Cruiser
2010 Hurricane Sundeck 2100

tiagobaracho

Hi sam.. would be great to have a compression tester that would give us an overall view of the problem.. If you have good compression, around 150 psi on all 4 cilinders we would know almost for sure that its not valve problems, not ring problems and not a need to rebuild. So it could be fuel not getting into the cylinder for some reason ( injector failure, or needing to be cleaned). throttle body can cause this problem but is not common.
Coils problems usually you can Hear that the engine is not burning correctly on idle or around 2k rpm.
Give us more information.. like... If you push full throttle with the ski out of water ( on flush hose sure) it will mark full RPM or will not , so it would be under load only?
How many rpm are you talking about when you say it does not reach full revs ? is it 5 6 7 k rpm ?
Are you sure the remote control low RPM mode is not activated ?

Ernest T

Minimum compression for the VX should be 164 psi, and a healthy engine will have over 200 psi on all cylinders.

__________________
2008 Yamaha FX HO Cruiser
2010 Hurricane Sundeck 2100

tiagobaracho

I fast read and I confused with two stroke, sorry.. but over 200 is high, not common on these yamaha 1100 engines...maybe on 1800 cc engines..
I have the Service manual on vx cruiser and it says:
Minimum compression pressure ( 164 psi)
So around 180- 190 is a good engine. Too much , may be carbon deposits...

My ski is a vx cruiser 2007 and is running perfectly and has a clearance of 0.11mm piston to cylinder wall and new rings.. For intent of educational video, I will do a video of the compression test on Saturday and post here the results.

Ernest T

Bet you a 6 pack you will see over 200 psi on all cylinders if its in good shape. I just checked my brothers 06 a couple of weeks ago, and it showed over 200 on all but one cylinder, and it was 195. Be sure to check it after you have warmed the engine......you get faulty readings on the MR1 due to the way the valves seat unless the engine is warm. Also be sure to hold the throttle wide open.

__________________
2008 Yamaha FX HO Cruiser
2010 Hurricane Sundeck 2100

Ernest T

As a side note, I looked up the last compression numbers I got on my FXHO at 124 hours: 208, 205, 210, 203. I haven't checked them this season, but probably will in the spring when I change the plugs.

No worry about carbon on these engines before 500 hours. I run Yamaha Ring Free Plus in every tank, so I doubt I'll ever see any carbon build up.

Also the new 1800 cc engines on the post 2009 FX, SHO, and FZR/S are totally different beasts. Minimum compression on those engines is 86.8 psi, and a healthy engine will have numbers around 130 psi. Compression values typically have little correlation to HP on these modern 4 strokes. Compression ratios are a different story.

__________________
2008 Yamaha FX HO Cruiser
2010 Hurricane Sundeck 2100

tiagobaracho

Lol.... 6 pack...
I thinkl i know what happened... When i checked my engine it was still out of the jet ski and i hadn´t run yet the engine... and since there wasnt nothing electric plugged, i just jumped the start motor to see the compression.... and the throttle was closed...
as i said... i will post a video saturday about this results of the compression test of my vx cruiser after warm up the engine and full throttle applied. I guess I will get a compression around 200 as you said..
But as a reference, the service manual really says that the minium acceptable compression is 164 psi..

Thanks guys for the input and saturday night i will post the video to prove me wrong ! hehehe

tiagobaracho

ernest, i wish i had access to Yamaha Ring Free Plus.... it´s impossible to get it here..
Do you have an endoscope ? would be a nice to do a video of your engine after 124h using Yamaha Ring Free Plus to see what kind of carbon build up situation there is...

Ernest T

I don't have a scope, but there is a guy that owns a rental business who just recently tore down one of his VX skis at 1800 hours. The ski was still running, but sluggish. He found carbon locked piston rings and valves. Now he is doing a test with some of his rental skis using the Ring Free. He is going to tear down thoses skis and post a report. It should be interesting. He is trying to see if the Ring Free will remove Carbon from engines that already have 1000+ hours. We already know that it will prevent carbon build up if you use it regularly, since it has been around for like 20 years for outboard motors.

__________________
2008 Yamaha FX HO Cruiser
2010 Hurricane Sundeck 2100