Yahama 30, 2 stroke 1997 - No hi speed!

[Captcweed]

This electric start engine has been running great no tell tail problems. Ran fine all the way out fishing. Re-started to return and engine started OK but cut off when put in gear 3 times. No prop restrictions. I used the idle advance lever on the shift to raise the RPM's, worked well went back to idle OK. In gear OK. When I started to run. . . No Power or very little all the way to full throttle, just a bit above idle speed. <br />The engine does not shake, spit sputter runs fine at slow or idle speed.<br />Got home connected the flush and started engine runs good. Put it in gear and ran the rpms up and it worked fine . . . back to the ramp for test and it's still doing the same under load. No power?

 

[jim dozier]

Re: Yahama 30, 2 stroke 1997 - No hi speed!

Check to see if engine is running on all cylinders. Pull spark plug wires 1 at a time (ground the loose wire) and see which one isn't pulling its load. Then check for spark on the offending cylinder. If you have a good spark, check carb on that cylinder, you may have a plugged main jet.

 

[Captcweed]

Re: Yahama 30, 2 stroke 1997 - No hi speed!

I did as you said had to wait for the weekend. With the top plug wire disconnected engine won't start. With the center plug wire off engine starts good, runs. With the bottom plug wire off engine won't start. Does that say the offending cylinder/ carb is #2 ?<br /><br />I also checked the fuel pump diaphram and it's good. The plugs all look the same no carbon just a bit damp w/fuel. Cleaned and replaced.<br /><br />What next?

 

[jim dozier]

Re: Yahama 30, 2 stroke 1997 - No hi speed!

Sounds like #2 isn't pulling its weight. Now you have to figure out if spark or fuel is the problem. If you haven't already checked, check the spark on #2. Inexpensive spark testers are available at auto parts stores. If the cylinder has spark check the fuel. Try squirting some premix in the carb throat of #2 cylinder and see if the engine picks up a little. If so you are probably going to need to rebuild the carb. I would do all of them at once.<br /><br />You will have to test the engine in gear and under load. They will start and idle in neutral on the muffs with only 1 cylinder working. Revving it in neutral in the driveway won't tell you anything.

 

[Captcweed]

Re: Yahama 30, 2 stroke 1997 - No hi speed!

A spark tester shows a good spark at all plugs.<br />Before I do the fuel under load shot in the throat test. <br />Is a bad cylinder, say rings a possibility for this problem from what you have heard on this so far?<br /><br />Is a compression test in order? I've looked at Yahama's exploded parts catalog and a carbs. rebuild looks like a nightmare.<br />Is bad cylinder a worst case senario? <br /><br />And this is something new, don't know if it's related.<br />During starting the engine for these tests. It has become slow cranking like a low battery. And the pos. + wire has become hot - HOT. But the battery charger hooked up is being asked for very little charge am I becomming paranoid?<br /><br />Trying to supply as much info as possible.

 

[jim dozier]

Re: Yahama 30, 2 stroke 1997 - No hi speed!

A compression test is always a good idea. I'm betting the numbers will be OK. Post them here if you do a test. Bad rings or a bad cylinder would be a worst cas scneario and your description does not sound like that would be the cause.<br /><br />Despite what the exploded diagram looks like, I'm going to go out on a limb since I've never seen the inside of a Yamaha carb, and say that I don't think a rebuild is that complicated. Most OB carbs are similar in design and construction. You will be removing the carb, taking off the float bowl, unscrewing and cleaning the main jet and idle orifices, and replacing the float valve (which is underneath the float and comes as a unit). The hardest part is usually getting the crap out of the way so you can unbolt the carbs. It isn't rocket science but a manual is advisable for a step by step procedure. My guess is that #2 carb has a clogged main jet.<br /><br />Which cylinder is the fuel pump attached to?<br /><br />I would check the tightness of your battery cables at all connections including the starter motor and solenoid. A loose positive or ground wire and continued cranking can heat up things.

 

[Captcweed]

Re: Yahama 30, 2 stroke 1997 - No hi speed!

Re-tightened all the battery connections and there must have been a weak point somewhere<br />because it cranks solid now, thanks.<br /><br />Did a compression test this morning 120 to 125 at each cylinder. So it's on to the fuel spray test later this week. <br /><br />Since the fuel filter and fuel pump, gas tank and fuel lines are as clean and free of varnish or grud as they are it's hard to think varnish in the jet of a carb. The fuel filter mesh is soooo fine. And the engine has at the longest sat for two, 2 week periods without use, and ran good between those, but it was recent. I did not run fuel out each time. But you can bet I will each and every time from now on. Well, gonna take a look see it seems. Is there anything else I should keep in mind as I have these babies apart. <br /><br />I know I'm showing my age here but use to be that floats in the carbs were light weight copper or nickle sheet solder sealed so they floated and sometimes they got a pin hole that let fuel fill them up and caused trouble like this? <br /><br />This forum is great and jimd your very helpful. My son and I are learning about these horses that take us to the playground fishin.

 

[Captcweed]

Re: Yahama 30, 2 stroke 1997 - No hi speed!

Forgot this from your last post... the fuel pump is on the #2 carb.

 

[jim dozier]

Re: Yahama 30, 2 stroke 1997 - No hi speed!

I asked about which cylinder the fuel pump was connected to because a leaking fuel pump diaphragm can kill the cylinder that it is attached to. But you said you checked the diaphragm (there should be 2, if you went to the trouble to look at them you should have replaced them, they're inexpensive) and it was OK so I will go back to the carbs.<br /><br />If the squirt in the throat picks the engine up, check the carb float valve for sticking closed. If the squirt in the throat doesn't help it could still be the carb float sticking open and flooding the cylinder, either way you should check the carb. I think most floats are plastic now but I don't know. Usually its the valve sticking open or closed but a float plastic or otherwise could leak and become gas-logged. If you go into the carbs go there with a rebuild kit and replace the parts that come in the kit. Anytime you go to the trouble to get in there and look replace the parts and gaskets.<br /><br />If the carb rebuild doesn't fix it rebuild the fuel pump. If you have spark and compression which you apparently have it has to be either to much or too little fuel and the carbs and fuel pump are primary culprits for cylinder specific problems. The only other item is the reed plate which you can visualize when you pull the carbs, look for bent, damaged, or missing reeds.

 

[Captcweed]

Re: Yahama 30, 2 stroke 1997 - No hi speed!

We did the shot in the throat test the result suprised me. Started with the #2 center carb. because it was the suspect. I used only a mist of starting fluid ( a whif only ) while running full throttle which is smooth but only just above slow speed zone.<br />The result was like a cough or baulk so I tried #1 at top, same result. Now I'm thinking oh no this is not the problem I bet. Now what? So next tried cylinder #3 and instant lurch full RPM for a second or 2. No doubt about it just like you said it was very pronounced. #3 is where the fuel problem is for sure. Am I right about this . . . you cannot remove and rebuild just one carb. And would you say it is not desireable to do only one. Even though only #3 is the drag. And we don't know why yet.

 

[jim dozier]

Re: Yahama 30, 2 stroke 1997 - No hi speed!

There's no law says you can't rebuild just 1 carb. But since you have to take a bunch of crap off of the engine usually just to get to the carb; and you have to get all your tools out; and the thing that crapped out your carb may have affected all of them; many (but not all) people will buy enough rebuild kits for all carbs and do them all at once. <br /><br />Do a complete rebuild with complete dismantling of jets, soaking in cleaner, using compressed air, and new parts and gaskets. Then if it doesn't work you know its not the other carb and you can move on to eliminating other items.<br /><br />If you read enough of these forums you'll find a common thread where people have a problem, get advice, and then partially execute the advice and confuse the issue and takes a lot longer to get to the bottom of the problem.<br /><br />I'm still confused though, it seems from your earlier test results with pulling the plug wires that #2 was a problem. You may find that both 2 and 3 work better after the carb rebuild, I hope so.

 

[Captcweed]

Re: Yahama 30, 2 stroke 1997 - No hi speed!

Right again Capt. And the Yahama Carb. rebuild kit for this engine comes complete w/three of each part necessary plus the fuel pump parts. Price is alot less than I expected. I'll post again when it's done and tested. ""Thanks for the good advice"". <br />May take some time getting the service manual which by the way is three times the cost of carb parts. But the linkage involved in breaking this down and re-construction, whew!. May need a step by step guide. Hopefully the new adjustments, valve etc. won't change the excellent running this engine did post, problem.