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  1. #1

    ALmost finished - 2001 GP1200r partial rebuild and upgrade

    Wow seems I've been working on this thing straight for 2 weeks! I hope my reward is spectacular, I also hope the rain doesnt wash me out this weekend

    What spawned the rebuild project was 12 year old carbs. Cold starting was terrible but once started the ski ran great. Some noticable hesitation in low/mid throttle but nothing too shabby. Upon disasembly found pop-off pressure over 95psi - OMG! Anyhow I wanted to have reliability on the same side as high performance, so I went ahead and planned for carb rebuilding, upgrading and hopping the ski's performance up at while keeping the dollar ammount still a good deal. While in there I upgraded jets, needle seat, mods, and springs to Onside bill specs. The main work was done to the carbs, but I added a few other goodies here and there listed below. Hopeing to hit ~70mph very very soon.

    Carbs and fuel supply:
    Genuine Yam Mikuni rebuild kits
    42~45psi pop-off
    110 pilot jets
    125 main jets
    1.5mm needles & seats
    Stripped and re-painted carbs
    New fuel line EVERYWHERE (BTW, Lowes home improvement has 20' of nice black/shiny fuel injection line on sale for $10)
    Doubled up each line connection with 2x 25lb zip ties (One forward, one backward on each connection)
    Removed fuel flapper (Previously)
    Replaced tank vent 1-way valve
    Replaced carb filters, cleaned out stock fuel filter
    Re-purposed 1 & 3's accel-pump for primer use (Shorty pull lever under seat)
    93 octane
    Amsoil Dominator (Race) premix 40:1
    Adjuster T-Handels


    The stock intake sucks. I mean, once you take it out its just plain terrible - and it cant even be submerged. I went with some new pieces here as well;
    Intake system
    Examined stock reeds in good spec
    Prok flame arresters
    Flame arrester adaptors
    Removed what I could of the stock airbox

    I wasnt going to break off the head, but got a great condition used head from a forum member sooooo - in it went!
    Engine
    Lowell cut high compression head (155psi? -Still need to comp test this)
    Added an RPM gauge
    New plugs

    Wasnt planning on doing anything to the exhaust, but since I got the head I figured I had to open it up:
    Exhaust
    Added home-made 3.5" 1/4" thick aluminum free-flow exhaust tube (11" long tube btw)
    Double & Trippled up the host clamps back there (All new clamps)

    I was torn between what to do with props, they're quite expensive, require a few big tools, ad not knowing what to get. Everyone gets SC 13/19, but I kinda was thinking of going with a 13/20 for mild top-end increase. Then I scored a SC 13/19 from a member here in excelent condition
    Under/Prop area
    Solas Concord 13/19

    I hope this works out. I've got a plug wrench on the ski and plan on testing at least every 1/4 throttle position the first time out starting with a decent idling in the no-wake. Hope it goes well



    Well, thats about it! Just about the only other things I can get/think of needing/wanting at this time are Leo's holeshot kit, and a jet-works mod.


  2. #2

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    Looks like you are on your way!

    Remember to leave you high speed adjustments fat and to stay focused on the low end until you get that right.

    Looks like a really good set up.

  3. #3
    Its not the lowest and highest end I'm worried about - I'm more concerned on if the 110/125 jets are too big/small. Thats a pain in the ass to get at again. I can adjust lows and highs a heck of a lot easier. than anything in the middle.

  4. #4
    ITS ALIVE!! It runs! Starting it the first time together wasnt so easy. Plugs were dry agfter several crankings. I'm thinking things were so dry inside the carbs/pumps/lines and engine that it was having a tough time getting suction and getting going. I applied a couple of psi on at the fuel tank for pressure but that didnt help. What got it going was about a tablespoon of fuel down each plug hole. Fired right up and stayed running. Priming like this worked likely cause it made the carbs pull hard on the tank. Success in restarting several times... and idled for a few minues total on the hose. Engine sounds freaking awsome - like a raged bull compared to before.

    I hope this sounds OK. Will dry carbs have trouble pulling in fuel the first time? I checked the 3 vent lines from the top of the reed cages to the carb pumps. They're connected just fine.


    After running for a bit; pulled the plugs. They were pretty wet but probably werent up to temp as well as the rest of the engine. On the hose. I still tightened the low screws in about a 1/4 turn. Restarted and set the idle on land to ~2k.

    Going to let it sit for the night; cool off. I'll try starting it again tomorrow to see how easy it'll fire. After, I'll run a compression test and see how the 155psi head measures up.

  5. #5

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    Quote Originally Posted by ZeroClient View Post
    Will dry carbs have trouble pulling in fuel the first time?
    Absolutely. Your whole fuel system was empty and needed to be charged. There have been forum members who have hooked up a primer bulb (that are used on outboard motors) to the return line on these engines to suck fuel from the tank all the way through the carbs to fill the carbs and the lines with fuel.

    If you still have the choke plates in or as I recall, you choose to leave the accellerator pump bulb in place as a primer, it should not be near as hard to start tomorrow.

    Stay focused on the bottom end first!!!!!!!!

  6. #6
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    nice

    i'm in the process of doing pretty much the same to my 02GPR...anxious to hear how yours runs this weekend. it seems most here have gone way beyond the simple mods/moved on to forced induction 4-strokes...lots of good info around though

    my carbs were a total mess- the pto carb had the regulator body rattling around (missing screws) lol...
    what did you use to strip the paint off your carbs? i've had limited success with soda blasting and gotta do something different

  7. #7
    Absolutely. Your whole fuel system was empty and needed to be charged. There have been forum members who have hooked up a primer bulb (that are used on outboard motors) to the return line on these engines to suck fuel from the tank all the way through the carbs to fill the carbs and the lines with fuel.

    If you still have the choke plates in or as I recall, you choose to leave the accellerator pump bulb in place as a primer, it should not be near as hard to start tomorrow.

    Stay focused on the bottom end first!!!!!!!!
    I removed the choke plates. I'm using the accel pump as a primer. It's crude - but I have a piece of wire attached the the pump's lever. Tug on the wire and it should prime; however it probably useless if no fuel is in the carbs Also when she finally started the idle adjust was set wayyy to high at 4500rpm. THis was probably me setting the knob on the bench when I was syncing the carbs. I've lowered rpms to 2000rpm out of water. I wonder if having the throttle plate open too far didnt help the dry-fuel-suck situation.

    Whats wrong with my bottom end? Interesting thing is; I've now got pretty low engine compression - even with the Lowell cut 155psi head: compression on all three is only coming up to only 85 psi. Previously the engine had 100psi on all three, and the piston crowns, cyl walls, cyl wash, and everything look great. I wonder if the piston rings are getting tired? I'm really hoping it's just fuel wash from putting some 40:1 mix down the plug holes. I did re-use my head gasket but it looked fine. Theres a lot of fuel on the plugs and seems to be running rich. Later today I'm going to run the test with a tablespoon of 2stroke oil down each hole. If that helps fix then I'll get it on the water this weekend - I hope.




    Quote Originally Posted by theprophet View Post
    nice

    i'm in the process of doing pretty much the same to my 02GPR...anxious to hear how yours runs this weekend. it seems most here have gone way beyond the simple mods/moved on to forced induction 4-strokes...lots of good info around though

    my carbs were a total mess- the pto carb had the regulator body rattling around (missing screws) lol...
    what did you use to strip the paint off your carbs? i've had limited success with soda blasting and gotta do something different
    To strip the Paint of the carbs, I used a PineSol dip for 48 hours. Anything stuborn after that came off clean with Aircraft Remover (Availabel at Autozone). Do pinesol first - it'll get 95% of the job. The aircraft remover will get the rest. If you have a powerwasher that may help but I dont.

    TheProphet: Look into getting some "YamaBond 4" or "ThreeBond 1211". I removed the reeds to check them, and the seals/gaskets were't as nice as I hoped. I replaced every gasket on the intake except those because they are not available to buy. Every gasket but those on the reeds. I did use assembly lube; but I wish I had used YamaBond4 or 1211 to form a good seal around the reed gaskets. I'm actually seriously thinking about removing everything to have some peace of mind with 1211/Yamabnd4. While running in the driveway yesterday the engine did have a couple instences of "floating rpm". It could be nothing but it could also be serious.

    Thanks guys!

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  9. #8

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    I do not think that the fuel will even detonate at 85 psi. Try a different pressure gauge.

  10. #9
    Quote Originally Posted by salty View Post
    I do not think that the fuel will even detonate at 85 psi. Try a different pressure gauge.
    I've tried two guages - a rental from Autozone and an old-school Snap-on gauge. The snapon registers right on a pressure test, but of course now I'm doubting everything. Its running and starting great. This morning I had to hit the accel/prime twice and it fired up in ten seconds. Ran great; runs excelent on hose. Cant wait to take it out on the water

    At the end of the day I know what I should do - full engine rebuild top to bottom; but can I just get a top-end gasket kit and re-ring the stock pistons before summer ends? I dont mind doing full engine breakdown and redo during off-season, but summer is going fast

  11. #10

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    I'm still not convinced that you have a compression problem at all.

    Get a good reliable/verifyable compression gauge
    strong battery
    throttle wide open
    spark plugs in the two holes that you are not testing
    test both cylinders twice

    If you are anywhere near 150 psi like you expect on each cylinder, tune it up and ride it like you stole it.

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