trouble starting my 426

[lee-yzf426]

its allways started 1st 2nd kick hot or cold , but the last two times ive ridden it its getting harder to start then, today it just didnt want to start when i eventually got it going it was running as sweet as a nut , then everytime i needed to start it would take about ten mins to get it fired up , i think it keeps flooding it self, well its seems that way anyway, if i turned the petrol off kick it over then it would fire up then id quickly switch the fuel back on and it be fine and i had to start it like this a few times , could it be that it needs a new plug or its running to richi dont know , i havent got much of an idea about whats is wrong so any help from you guys here would be much appreciated ,

cheers lee

[grayracer513]

Could be you have a float needle leaking slightly, letting the float level creep up and make the bike slightly rich or flooded. Good place to start.

[lee-yzf426]

Could be you have a float needle leaking slightly, letting the float level creep up and make the bike slightly rich or flooded. Good place to start.

i aint got a clue what a float needle is if im honest lol , where is the float needle on the card is it? could it not be a case of a bad/worn spark plug or could it be something a bit more serious ?

[grayracer513]

The float needle is inside the float bowl of the carb, and should be looked at by someone who at least knows what it is. The 426 is touchy about spark plugs, though, and it can't hurt to try a fresh one.

[arnego2]

Hi there

if it keeps getting worse valves could be the problem.

regards

Arnego2

[lee-yzf426]

right today i have had the spark plug out ( they couldnt of put it in a more awkward place lol) its quite black (burnt) no damage to the end , seems to be sparking ok although quite small sparks duno how big they should be , il put a fresh one in anyway when i get a chance , is this likely to be my problem or what ,

when you say valves could you explain more please i need this sorted asap

cheers

[Ryan426]

right today i have had the spark plug out ( they couldnt of put it in a more awkward place lol) its quite black (burnt) no damage to the end , seems to be sparking ok although quite small sparks duno how big they should be , il put a fresh one in anyway when i get a chance , is this likely to be my problem or what ,

when you say valves could you explain more please i need this sorted asap

cheers

He means your valves could be out of spec. They need to be checked every so often. I just had mine checked a month ago and even though my bike ran ok I had 2 intakes that were tight. Now my 426 runs awesome.

[jcm3]

Assuming that you didn't change anything, I agree that it could be a plug. I've had to replace mine a few times (not very often), because all of a sudden be a b!tch to start. After the plug, it would fire right up.

The reason I asked if you changed anything was because I recently changed out my pilot jet and throttle cable. I know these bikes are touchy about that stuff. I changed out the pilot because I mistakenly thought it was larger than stock due to some writing in the owners manual, and due to some behavior that led me to believe it was too big.

After the change, I had a helluva time starting it until I realized that my old cold starting technique, which started with two pumps of the throttle, was flooding it. Now, no pumps, and it will start after sitting for a month or so in a few kicks.

[lee-yzf426]

nope ive not changed a thing on the bike all totaly standard as far as im aware , and my starting technique is no twists of the throttle, kick over a few times ,find top dead centre and then kick it and it starts first second kick everytime , well it used to anyway.

right today i put a new plug in and still she wont start , its backfiring like mad ( sounds like a gun shot lol ) and she definatly flooding because it absolutly stinks of petrol , what should be my next move now , what should i do,

and how do you go about checking the valves is this something that should be left to a mechanic to check , also how much would this cost roughly,

sorry about all the newb questions but i really want the beast fixed asap

cheers lee

[lee-yzf426]

little update,

ive just had the bike running , it started with the fuel off then i switched it on and let it tick over to warm up when it was warm i tryed starting it again and it wouldnt start, i turned the fuel back off and it started again straight away any ideas as to whats causing this ?

[grayracer513]

Yes.

Read: https://www.thumpertalk.com/forum/showthread.php?p=9643612#post9643612

[lee-yzf426]

gray im assuming you think its th efloat needle yes?

could you shed some light on how to solve this problem please like what needs to be adjusted because ive spoke to a bike shop and they think its the valves so i could save my self from taking it in there for repair tof ind out the valves was ok , so could you explain roughly what i need to do

cheers lee

[grayracer513]

The bike shop hasn't heard the part about turning the gas off, apparently. Either that or they need to quit fixing bikes and open a doughnut shop.

The carb has a float bowl under it from which the various metering jets draw fuel. The level of the fuel in the bowl must be carefully controlled; too low, and the fuel is too hard to raise into the air stream flowing through the carb; too high, and it's too easy to get more than you should have. If it's enough too high, it will flow right into the engine without being invited.

The level is controlled by a float hinged to the carb body. As the fuel level rises, the float rises with it, until it finally bears against a needle valve that shuts off the incoming fuel. As fuel is drawn out of the bowl, the float drops to let more back in.

Your problem appears to be that the fuel level is not being managed by the carb float, which requires you to turn it off in order to prevent it flooding while you start it. I wouldn't be surprised if you told me that if you leave the gas on long enough with the engine off, fuel will drip on the ground under the bike. This is likely to be caused by one of a few things related to the float needle and the brass seat it seals against:

1. There is dirt in/on the needle seat. We're not talking about course sand here. It could be barely visible, or even smaller. Remove and gently clean the needle and its seat.
   
2. The rubber tip of the needle is worn, damaged, or dried up and cracked. Replace the needle and seat.
   
3. The O-ring that seals the needle seat to that carb is shrunken or cracked. Replace it.
   

[lee-yzf426]

So how would I go about cleaning , adjusting , the needle obviously take out the carb to start with, then what ?

Lee

[arnego2]

Hello there

Hard start can be related to valve tightening and here is a video of a kxf250 valve adjustment. It is not really difficult to do it and has to be done pretty frequently when riding hard. Every 10 to 15 hours I check mine. video

Other than that I found the air screw on the carb is also quite important when it comes to starting. A fourth of a turn can make a difference. Mine, a yz450f is out about 2 turns.

Good luck

Arnego2

[grayracer513]

So how would I go about cleaning , adjusting , the needle obviously take out the carb to start with, then what ?

Lee

Service Manual: http://www.yamaha-motor.eu/eu/services/owner-manuals/index.aspx

[snomopro]

Try looking at the hot start plunger. Mine started hard when I got it and when I finally got it started it popped like crazy. I pulled the hot start plunger in and out a bunch of times and the next time I started it it fired right up with no popping. Not sure how the hot start plunger works though. Just a thought.