2018 YZ450F Problems Round 2

damn man, sorry to hear all the problems with a new bike. I'd be devastated. possibly something fuel related? Pump, fuel flow, bad valve in gas cap? I'm no expert but just throwing out ideas.

It’s normal. When a thumper is hot, it needs the throttle turned a bit to fire up. Our bikes do not have a choke, the button we push opens the throttle a bit, myself I just open the throttle myself and voila fires up no problem in gear or not hot or cold

Ugh that sucks, things like these tend to steer people away from brands. Hoping you'll get it sorted without dumping cash into it as Yamaha really should help you out.

Id look at your fuel pump and injector.

Also might look for a different color bike. The probs youre having and yamaha being of basically no help is horse shit. Valves out of spec at 12 hours?!? Dude my 250f has 15 on it and the valves are right where they were when i built it. Sounds like a dud of a bike. For real man hate to hear that.

So it is electric start, right?
Have you load tested the battery?
The OEM batteries in these bike are junk and do not last any time.
I suspect that the battery voltage drops off under load ( like cold starting), but still has enough juice to start a warmed up engine. Also if the battery has a loose plate in it, it will cause the engine to stall.

Paw Paw

Dang... sorry to hear about the issues. 60 hrs on mine, not a single glitch. Some good, some bad I guess

Any updates?

rollin64caddy wrote:

Any updates?

Ended up being that the fuel connector clip was broke. This was making it move in and out which is what we believe caused the bog. We thought we figured out the problem and I went out riding and the connector complete came lose (almost throwing me over the bars...was very lucky). Pushed the bike back to the truck and tried starting it and it began pissing gas...that's when we realized that the connector had let go. We put a few zap straps on it and it has been working fine since (knock on wood).

How this happened I have no idea. Whether it was when the new motor was swapped, or if the fuel tank was moved the wrong way when we did the valves. Either way this bike has been very frustrating.

rollin64caddy wrote:

Any updates?

foreman52 wrote:

Ended up being that the fuel connector clip was broke. This was making it move in and out which is what we believe caused the bog. We thought we figured out the problem and I went out riding and the connector complete came lose (almost throwing me over the bars...was very lucky). Pushed the bike back to the truck and tried starting it and it began pissing gas...that's when we realized that the connector had let go. We put a few zap straps on it and it has been working fine since (knock on wood).

How this happened I have no idea. Whether it was when the new motor was swapped, or if the fuel tank was moved the wrong way when we did the valves. Either way this bike has been very frustrating.

nothing worse then not trusting a bike when you ride it. Maybe sell this one and hop on a 19?

foreman52 wrote:

Ended up being that the fuel connector clip was broke. This was making it move in and out which is what we believe caused the bog. We thought we figured out the problem and I went out riding and the connector complete came lose (almost throwing me over the bars...was very lucky). Pushed the bike back to the truck and tried starting it and it began pissing gas...that's when we realized that the connector had let go. We put a few zap straps on it and it has been working fine since (knock on wood).

How this happened I have no idea. Whether it was when the new motor was swapped, or if the fuel tank was moved the wrong way when we did the valves. Either way this bike has been very frustrating.

Id replace that line ASAP. Also, valves out of spec at 12 hrs? Dayum! I have a '18 CRF450RX with 30 race hours (including a race where I lost 50% of my coolant) and 9 trail hours...my valves have not moved at all

hopefully problem solved and now you can enjoy the bike. good luck man.

rollin64caddy wrote:

Any updates?

foreman52 wrote:

Ended up being that the fuel connector clip was broke. This was making it move in and out which is what we believe caused the bog. We thought we figured out the problem and I went out riding and the connector complete came lose (almost throwing me over the bars...was very lucky). Pushed the bike back to the truck and tried starting it and it began pissing gas...that's when we realized that the connector had let go. We put a few zap straps on it and it has been working fine since (knock on wood).

How this happened I have no idea. Whether it was when the new motor was swapped, or if the fuel tank was moved the wrong way when we did the valves. Either way this bike has been very frustrating.

fourfourone wrote:

nothing worse then not trusting a bike when you ride it. Maybe sell this one and hop on a 19?

Looking into a new Honda for 2019!

rollin64caddy wrote:

Any updates?

foreman52 wrote:

Ended up being that the fuel connector clip was broke. This was making it move in and out which is what we believe caused the bog. We thought we figured out the problem and I went out riding and the connector complete came lose (almost throwing me over the bars...was very lucky). Pushed the bike back to the truck and tried starting it and it began pissing gas...that's when we realized that the connector had let go. We put a few zap straps on it and it has been working fine since (knock on wood).

How this happened I have no idea. Whether it was when the new motor was swapped, or if the fuel tank was moved the wrong way when we did the valves. Either way this bike has been very frustrating.

harescrambled wrote:

Id replace that line ASAP. Also, valves out of spec at 12 hrs? Dayum! I have a '18 CRF450RX with 30 race hours (including a race where I lost 50% of my coolant) and 9 trail hours...my valves have not moved at all

I had a 16 YZ250F both intake valves went at 21 hours and again at 48. Thought it was a lemon since I had not heard or seen anyone around having valve problems with their Yamaha's so I purchased a 17 YZ250F. Valves went in that at 37...which isn't that bad...but still no one around the track on any brand was having that kind of trouble. I have learned my lesson this third time around with my 18. The next one will certainly be a different colour!

rollin64caddy wrote:

hopefully problem solved and now you can enjoy the bike. good luck man.

Appreciate it my man! Thank you

Bought a new 2019 YZ450F 6 weeks ago, after 8 hours it wouldn't start, checked the inlets valves and they were totally tight so took it into my local dealers for setting. Loads of sand in the inlet manifold and throttle body so I put it down to my bad maintenance and over enthusiastic use of the power wash.

Needed a new barrel,piston, 4 valves, any how £1400 later and its back together again.

Ran it today for one hour at a sand track, air filter edges greased, sock over the filter, total care when washing it down.

Just got it back and very carefully stripped the filter and housing off and the there is sand in the inlet manifold and throttle body, what are you supposed to do? This thing is going to be broken again after a few more hours running.

Starter clutch also went at 8 hours although Yamaha did fix this under warranty, seriously considering getting shut.

AndyH wrote:

Bought a new 2019 YZ450F 6 weeks ago, after 8 hours it wouldn't start, checked the inlets valves and they were totally tight so took it into my local dealers for setting. Loads of sand in the inlet manifold and throttle body so I put it down to my bad maintenance and over enthusiastic use of the power wash.

Needed a new barrel,piston, 4 valves, any how £1400 later and its back together again.

Ran it today for one hour at a sand track, air filter edges greased, sock over the filter, total care when washing it down.

Just got it back and very carefully stripped the filter and housing off and the there is sand in the inlet manifold and throttle body, what are you supposed to do? This thing is going to be broken again after a few more hours running.

Starter clutch also went at 8 hours although Yamaha did fix this under warranty, seriously considering getting shut.

What filter oil are you using? Checked for cracks in the airbox/manifold i assume?

Get the Twin Air setup with the new cage and more rounded filter.

AndyH wrote:

Bought a new 2019 YZ450F 6 weeks ago, after 8 hours it wouldn't start, checked the inlets valves and they were totally tight so took it into my local dealers for setting. Loads of sand in the inlet manifold and throttle body so I put it down to my bad maintenance and over enthusiastic use of the power wash.

Needed a new barrel,piston, 4 valves, any how £1400 later and its back together again.

Ran it today for one hour at a sand track, air filter edges greased, sock over the filter, total care when washing it down.

Just got it back and very carefully stripped the filter and housing off and the there is sand in the inlet manifold and throttle body, what are you supposed to do? This thing is going to be broken again after a few more hours running.

Starter clutch also went at 8 hours although Yamaha did fix this under warranty, seriously considering getting shut.

Lynch wrote:

What filter oil are you using? Checked for cracks in the airbox/manifold i assume?

Putoline filter oil and plenty of it. Just had a better look at it and found a couple of things.

Firstly the filter has two holes in the middle of it where the spike goes through, interesting! Maybe I did it but I think that might be unlikely, irrespective though the filter had a sock over the top of it so I wouldn't have thought that would have let any sand through.

I had also greased the seat that the filter sits on. On the bottom edge the grease was full of sand which would suggest that the filter wasn't seating properly on that edge. Why that should be I have no idea and need to have a better look at it.

Having read this forum and others what does seem apparent is that a lot of YZ450 owners are suffering from tight inlet valves that are out of adjustment and hence bad starting. The most logical explanation for this is the wear caused by sand which is somehow getting into the manifold.

I would be interested to hear from any other YZ450 owners to know if they remove the metal filter gauze below the air filter is there any sand in the inlet manifold? It also seems to accumulate on the edge of the throttle butterfly valve which is visible down the manifold.

mx317 wrote:

Get the Twin Air setup with the new cage and more rounded filter.

Cheers I'll check that out

AndyH wrote:

Putoline filter oil and plenty of it. Just had a better look at it and found a couple of things.

Firstly the filter has two holes in the middle of it where the spike goes through, interesting! Maybe I did it but I think that might be unlikely, irrespective though the filter had a sock over the top of it so I wouldn't have thought that would have let any sand through.

I had also greased the seat that the filter sits on. On the bottom edge the grease was full of sand which would suggest that the filter wasn't seating properly on that edge. Why that should be I have no idea and need to have a better look at it.

Having read this forum and others what does seem apparent is that a lot of YZ450 owners are suffering from tight inlet valves that are out of adjustment and hence bad starting. The most logical explanation for this is the wear caused by sand which is somehow getting into the manifold.

I would be interested to hear from any other YZ450 owners to know if they remove the metal filter gauze below the air filter is there any sand in the inlet manifold? It also seems to accumulate on the edge of the throttle butterfly valve which is visible down the manifold.

Stock filter? If so throw it in the trash, you need one with the rubber grommet. Twin Air for example.

I'll check with a few people I know that ride the 18-19 450 Yamahas and see if they have had any problems. Probably 500hours between three people, two of them rides heavy sand 90% of the time.

Yes stock filter, bikes only done 8 hours but already had a barrel/piston and valves, appreciate any help or advice, can't afford to break it again.

My 19 250f has to have starter clutch replaced at 4 hours too

I just recently found a little sand in the air boot area on my sons 19 250f.We have 4 hours on it and I’ve been paranoid about that filter/cage since the day I saw it. I also had the filter well oiled,greased and had a filter skin on it. I said that’s it and bit the bullet for the twin air cage and filter set up at $250 ! Hated spending that much but this set up seems way safer. The twin air set up goes back to the cage under the filter. The filter has the rubber grommet with the bolt instead of that stupid cage on the outside with the tabs sliding over to hold the cage down. Unfortunately winter came a little early so we haven’t got to try this system out to see if it’s keeping the sand out. Also I checked the valves and they are exactly the same as the day I brought it home so hopefully our worries are over. Other than that,this bike is amazing.

Ordered a Twin Air filter and cage, so ill check the manifold for sand again after I've fitted it and post the results here

Also another cool thing about the twin air is that the base has a lip on it. So the filter sits down over the base. You’ll see what I mean when you get it. Much better design to keep dirt out.

AndyH wrote:

Yes stock filter, bikes only done 8 hours but already had a barrel/piston and valves, appreciate any help or advice, can't afford to break it again.

I have a 2016 450FX and I bought some foam filter material from McMaster-Carr, Part no. 9803K305 for $15. Its dark gray 12in X 12in X 2in thick. I cut it to fit in the intakes and stick out about 1/2in. There are couple drain areas on the inside of the air box where I also I installed it. You can run them dry or apply some light oil. They keep out the course sand leaving the filter inside to deal with the finer dust. This filter material is not really tight, so I haven't noticed any power loss but it does help keep the filter cleaner. I use twin air filters, Bel Ray oil and change the filter every ride. For the last two years its been working well for me. It will be interesting to hear how the twin air system works for you. If you're having problems with your engine getting dusted, anything is worth a try.

AndyH wrote:

Yes stock filter, bikes only done 8 hours but already had a barrel/piston and valves, appreciate any help or advice, can't afford to break it again.

like2ride wrote:

I have a 2016 450FX and I bought some foam filter material from McMaster-Carr, Part no. 9803K305 for $15. Its dark gray 12in X 12in X 2in thick. I cut it to fit in the intakes and stick out about 1/2in. There are couple drain areas on the inside of the air box where I also I installed it. You can run them dry or apply some light oil. They keep out the course sand leaving the filter inside to deal with the finer dust. This filter material is not really tight, so I haven't noticed any power loss but it does help keep the filter cleaner. I use twin air filters, Bel Ray oil and change the filter every ride. For the last two years its been working well for me. It will be interesting to hear how the twin air system works for you. If you're having problems with your engine getting dusted, anything is worth a try.

Well after a bit of searching I have managed to aquire a Twin Air Pro filter kit for £200 that not only replaces the filter but the plastic cage and adapter plate onto the inlet manifold. It is a very well made piece of kit with an alloy frame and a lip that secures the filter onto the housing. Filter now screws down with a central alloy bolt through a rubber sleeve.

Will be giving it a go this weekend, fingers crossed it solves the problem. 'll let you know.

I asked around, 5 people, none of them have had any problems with the bikes letting sand/dirt bye. All used Twin Air filters, different oils: No Toil, Bel-Ray, Putoline.

I was worried at first but no problems so far.