gp1200 engine issues
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- เผยแพร่เมื่อ 5 ก.พ. 2025
- This part in 2 stroke engines is often overlooked. But is important for the 2 stroke to run properly. This is what problems I found in both of Jasons gp1200 engines. So neither one was working quite right. gp1200 engine issues. Bad reeds or reed valve. Or to say reed valve problems. And I am not impressed with the aftermarket reeds I found in this engine. They are total junk.
Have you done the fuel pump pressure equalisation mod ? GreenHulk goes into detail on how it’s done , also you need to fill in the grooves in the inlet manifold that joins all three inlets together. This improves the signal ( vacuum) to each carb at high speeds to stop 🛑 the carbs running lean . Makes the engine run better and more reliable too . While you’re at it , do you want some porting specs on the exhaust ports on the 65U engine ? This engine has serious exhaust port area deficiencies that kills the potential of the engine and extra rpms . Let me know and I can email pictures and exact measurements. Regards Adam
any info you can get me would be great. Especially on the 1200r since I just got a couple of them.
@@JetSkiBrothers the GP1200R has some must do reliability upgrades that you should do. 1
Fuel pump equalization mod that lets the all 3 fuel pumps share the job of maintaining fuel pressure. The return hole in each carb is drilled out with a 1/8 drill . A 95 main jet is placed in the outlet of the return line to the fuel tank in the carb that the throttle cable attaches to. 2 The cross over ports under the carbs in the inlet manifold must be blocked off with silicone. This improves vacuum signal in the carbs for much better jetting and prevention of lean seizures. 3 The powervalves need wave eater retainer clips installing, this prevents them from coming lose and damaging the engine. The plastic powervalve joiners need to be replaced with a solid joiner that ensures all 3 valves open and close at exactly the same time. This is really important ! It stops the PTO cylinder from working harder than the first 2 cylinders because they don't have full opening of the valves due to flex in the stock plastic joiners . Yamaha must know these things wear out eventually and cause the engine to fail . 4 carb jetting. 110 pilots and 120 mains ,1.5 needle and seat ,95 gram springs. 1 turn out on lows . 1 1/2 turns out on highs .
Keep the choke plates and use aftermarket flame arrestors
The GPR likes more compression, the head can be machined. 38 cc domes will be pump gas safe using 92 octane fuel. 150 psi . I have my own lathe and mill to do this work . Do you have anyone able to do this ?
I have an Advent 1290 ignition using the 84 curve and 7800 rpm rev limit and powervalve settings snap 58 . The stock CDI opens the valves more slowly than the Advent 1290 so caution must be used with compression with the stock cdi
You can use the exhaust system from an 05 or later GP1300R for another 10 hp with the powervalve engine.
The exhaust port can be widened to 56.8mm or 71% of bore if you want to go really fast. Caution here if you haven't done porting before on Nikasil cylinders. For the pump , a 14/20 Solas concord works with these mods , R&D gp800r scoop grate is the fastest and a R&D ride plate. Stock sponsons stepped up at the front and down in rear is best . Trim tabs spaced down 3mm on each bolt is a start . The stock nozzle is a 87mm dia , I use a GP1300 85mm nozzle for top speed , I also have a GP1800 nozzle that gives good acceleration. Buy a GP1800 steering nozzle too , plastic sucks when they break. That's a start ,but there's still more can be done . I have a Skat trak setback 158mm pump that is simply awesome 14/19 impeller, 7300rpm at 73mph ..I also have a fuel pressure gauge to check fuel flow . 1-2 psi at idle ,5-6 psi full throttle.
If you want more info ,send me your email address and I can send photos of porting and other pump mods .
Regards Adam
Hi Mate, why did all of that rusty water get in around the flywheel / bendix?
Question my jet ski is a Yamaha waverunner 1200 run fine on the trailer with the water hookup every time I back up to the lake jet ski die
When I pull out from the lake take a couple seconds and then the engine start again, if I let the engine running and back up to the lake again , the engine die again ,,,any idea ?
Stock reeds outlast any other reeds on the 1200 . If you have new reeds you can cut the old reeds about half way along and sandwich them on top of the new reeds under the metal stops . This adds stiffness at high speeds and still have a snappy sealing bottom end response .
I like it
That sounds good
Hey guys , just finished watching this video and I thought you might like to know some facts about reeds . The Reed stops on the GP1200 are set from the factory at 10.7mm from the tips of the reeds to the tip of the metal stops . Any more clearance results in reeds that flap at full throttle and don’t seal properly , you can lose 10 hp just from this alone . That’s why some engines are rockets 🚀 and others are slugs 🐌. Stock reeds are best for the long term , I have a reed spacer on my GP1200 that pulls the reed cages back 8mm from the crankshaft and increases crankcase volume too . It’s the little details that results in a really good engine performance. Have you guys done the fuel pump pressure equalisation mod to the carbs ? Stops the engine running lean on one cylinder and seizure from damaged fuel pump check valves..
excellent info
My a help ,wats grague off crash Yamaha gp 1200 2 stroke?
Hey do a show on the js550 with 440 pump. Go into details about if its worth it or not! I got a 550 that the needs a new shaft and impeller from some dumb chit damaging during removal. (I now know they are opposite thread imprllers!)
I am up in air on ordering parts or slap a 440 pump on with s stainless says skat track 5 5 on it.
TheShockLoad it’s on the way. And btw the 550/440 is a really great combination
@@TheShockLoad do the 440 pump, especially if you already have the parts. I was pleasantly surprised by mine, and I'd like to know if you get the same results.
Damn those reeds are shot for sure! Will you do oem for the new ones?
yeah went with oem
I just pulled off my intake to check my reeds and I’m not sure if they are shot. I can see a little light between the end of the reed and the body. Should there be no light at all? I thought my ski was running bad because I didn’t have my carb tuned right because I could only get it up to 22 mph on my 650sx with a 46mm carb. Low end was fine but it seemed like it couldn’t rev up all the way. Should I replace my reeds? Does that seem like the fix? Thanks.
Usually when your reeds are bad you get no bottom end at all.
Jacob Superjet Jet SKI ok thanks. I just flipped them around and put them back on. They look like they seal better.
@@Jacobskibros Curious to get your thoughts on this. I have a 99 Carb Polaris 1200 Genesis jet ski. When I give this throttle it bogs a little and funny as this sounds it sounds a little like a goose. Could that be a reed valve noise? I have my fingers crossed that's the case and its not a crank shaft noise.
@@wkualum3194 To me it sounds like you may need to clean the carbs, but it's hard for me to really know. Reeds? Maybe? doesn't hurt to check.
You can sell parts?
Not true not true put some oil on the reeds and look at them seal. also when piston is on down stroke there is pressure on the reeds that's not there when your looking on the bench. Yours may be junk aftermarket and someone probably way over tightened the screws because afraid would fall out. look at all the motox bikes that had them stock I have them in 3 bikes two outboard and two pwc's and they all idle like the well tuned machines they are. Ive installed so many in pwc bikes and outboard but I took the time to surface the cage flat. Idle quality twice as good with good fiber reeds. and I will never ever ever use the cheep aftermarket carb kits. I very seldom ever buy a kit anyway just new diaphragm from yamaha of coarse I never used carbon x reeds just boyseen and never ever ever over tighten the screws this will make them not seal. I torque them and use locktight. I have them in 3 of my classic bikes and my yamaha prov 150 and it idles so so good and smooth.
One of the gp 1200 motors 😂
It's times like that when I think about SMASHING that dislike button. ;)
yeah we got three lol
@@Weeble_Warbles oh don't hate us, you know we would share with you if you were around here.
@@JetSkiBrothers I know you guys would. I'm just envious of the deals you guys find.
@@Weeble_Warbles hey, just do it! We know you're on our team...and once you're on our team... (chuckling crescendos into voluminous, possibly evil laughter)