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foreman52
8/16/2018 5:44pm
8/16/2018 5:44pm
Edited Date/Time
1/4/2019 10:02am
Hey everyone, back again. For those that never saw the problems I've been having in my other fourm here is a quick run down:
- Motor replaced at 6 hours (3rd gear slipping and could never find the issue...5 weeks off the bike before Yamaha replaced the motor).
- Intake valves were completely out of spec and needed to be replaced (had no effect on 3rd gear).
- Starter clutch went at 4 hours on new motor.
- No warrenty/compensation from Yamaha.
- Just shimmed one intake valve that was so tight you couldn't get a 4 in it (roughly 12 hours).
I was just at a race this weekend and the bike completely bogged out before the landing off a jump (4th moto out of 5 for the day). I knew something wasn't right so I pulled off.
When I shut the bike off it wouldn't start again. I changed the filter, but nothing. When I pulled the choke out the bike would start. Without the choke it eventually began to start but backfire immediately.
The issue seems to happen when THE BIKE IS WARMED UP. Once it is warmed up it will not start without the choke/or start like a bastard.
THIS IS NOT AN ISSUE WITH THE STARTER CLUTCH. The bike starts fine after being warned up shortly with/without the choke. After it has been primed it is game over.
Has anyone had this problem yet?!
- Motor replaced at 6 hours (3rd gear slipping and could never find the issue...5 weeks off the bike before Yamaha replaced the motor).
- Intake valves were completely out of spec and needed to be replaced (had no effect on 3rd gear).
- Starter clutch went at 4 hours on new motor.
- No warrenty/compensation from Yamaha.
- Just shimmed one intake valve that was so tight you couldn't get a 4 in it (roughly 12 hours).
I was just at a race this weekend and the bike completely bogged out before the landing off a jump (4th moto out of 5 for the day). I knew something wasn't right so I pulled off.
When I shut the bike off it wouldn't start again. I changed the filter, but nothing. When I pulled the choke out the bike would start. Without the choke it eventually began to start but backfire immediately.
The issue seems to happen when THE BIKE IS WARMED UP. Once it is warmed up it will not start without the choke/or start like a bastard.
THIS IS NOT AN ISSUE WITH THE STARTER CLUTCH. The bike starts fine after being warned up shortly with/without the choke. After it has been primed it is game over.
Has anyone had this problem yet?!
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.
The Shop
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
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.
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.
Pit Row
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.
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.
Will be giving it a go this weekend, fingers crossed it solves the problem. 'll let you know.
I was worried at first but no problems so far.
I use No-toil filteroil and Twin airs normal filters (not the aluminium powerflow kit) and i haven't had any issues with dirt getting in. I was a bit worried about it when i have read quite a lot about this issue but i haven't experienced it at all.
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