Yamaha T9.9 Throttle/Carb adjustments

[gump218]

OK - I have my cooling water solved; the engine starts and runs at lower RPMs but bogs down like it's being choked when the throttle is advanced.. No manual choke... Timing belt marks all look (TDC 0 with Cylinder 1 at ^) consistent with the book.<br /><br />What needs to be adjusted to correct? This is a 1995 T.9.9EXHT 6G8UL 787273

 

[jrod8v92ti]

Re: Yamaha T9.9 Throttle/Carb adjustments

pg 29 tune up specifications<br />spark plug- nkg cr6hs <br />gap- .6mm/.024in<br />ignition timing at idle - btdc 5deg +/- 1deg<br />full advanced timing 35deg +/- 3 deg<br />carb pilot screw turns out - 3<br />idle speed in neutral - 950<br />intake vlv cold - (.15-.20mm)(.006-.008in)<br />exhaust vlv coldc - (.20-.26mm)(.008-.010)<br />tac setting - 6 pole

 

[gump218]

Re: Yamaha T9.9 Throttle/Carb adjustments

How do you adjust the timing.... Shift the belt one tooth? As it sits I am at TDC with number 1 at the ^. I see the mark for 5 btdc and 35...

 

[garyN]

Re: Yamaha T9.9 Throttle/Carb adjustments

I will bet you have a bad fuel pump. I think many of these yamaha did - or the gas we use did it. Check the diaphram. My engine did almost the same and the dealer kept cleaning the carb (and my wallet) until he checked the oil and found it overfull with gas!.<br /><br />Gary n

 

[the machinist]

Re: Yamaha T9.9 Throttle/Carb adjustments

I vote for the fuel pump. Not only the diaphram in the fuel pump, but also replace the check valve. Yamaha does not sell a fuel pump repair kit, so you need to order the parts separately. The check valve is a thin neoprene round, (about the size of a 25cent pc) that has 2 dog ears, one on each side. I have had to replace mine about every 3 years. The motor will start, but dies when you put it a load on it (like when you put in gear). One clue is that you may not be able to pump up the primer bulb to where it is hard.

 

[garyN]

Re: Yamaha T9.9 Throttle/Carb adjustments

And while your at it try calling Yamaha and tell them there is a problem. Today I was insulted by the customer service specialist in Georgia. <br /><br />When I told him that I was finding several others with problems in the fuel pumps from around the Y2K model year he said " and I could go in the internet and find people who where killed when a pyramid fell out of the sky on them!" This company needs an overhall and soon. As I told the dealer today "I should have bought a KIA! Stay away from the Yamaha at all cost. Looks like Honda is the only real way to go. <br />Gary N