Hmm now what (A Rebore!)
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@Calum heads really aren’t expensive I see them all the time for 30 pound but that said I’d be more than happy to run that head
@declan Cheap as chips mate.
£140 he wants for that 3MB.
Used to be able to get them for £30, but not anymore. You can only get restrictive 3BN heads these days. Which need money spent on them to bring the power back up. Which he could just do to his current damaged head.
These look unrestrictive, but I don't know if they fit.
If you find a 3MB for £30 in usable condition, buy it. Would be myt advice.
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Its back together and running. Not ridden yet, but let it get to temp and adjusted idle. Took about twenty kicks to start first, but now its starting first kick. Took a compression reading before I started the engine with the exhaust off
Pretty busy tomorrow, but If I get a moment Ill take it for a spin and see what is what
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That's odd. Why did it take so long to start?
You made sure the oil pump does not have any air in it and is operating correctly?
@Calum I'd adjusted the throttle too much so when I fired it idled around 7k I think was the reason. Took it out for 15 gentle miles yesterday and all seemed well, and took to work this morning, so far so good. Just trying to be gentle and keep the revs relatively low for the meanwhile and get some miles under her belt.
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My big bore Athena made 14 bar compression.
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Little update. After running it in a little and opening it up a bit, I wasn't particularly impressed. It felt worse than before up top. So I did mess with the squish too much I think. Luckily managed to get another 3mb head in a more normal condition for £25 and have just fitted it and compression tested it and its up, so hopefully tomorrow's ride will be an improvement.
Now I have the old head here may as well look into getting it sorted properly at some stage and swapping back later down the line.
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Little update. After running it in a little and opening it up a bit, I wasn't particularly impressed. It felt worse than before up top. So I did mess with the squish too much I think. Luckily managed to get another 3mb head in a more normal condition for £25 and have just fitted it and compression tested it and its up, so hopefully tomorrow's ride will be an improvement.
Now I have the old head here may as well look into getting it sorted properly at some stage and swapping back later down the line.
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Little update. After running it in a little and opening it up a bit, I wasn't particularly impressed. It felt worse than before up top. So I did mess with the squish too much I think. Luckily managed to get another 3mb head in a more normal condition for £25 and have just fitted it and compression tested it and its up, so hopefully tomorrow's ride will be an improvement.
Now I have the old head here may as well look into getting it sorted properly at some stage and swapping back later down the line.
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@Calum It had a few small nicks, but was a whole load better looking than the other. Got it from where I bought the bike, it was the best 3mb he had, got loads of the more restrictive ones though.
Sadly no snaps NINJA, I think maybe it's a slightly older head as it had 3mb and Yamaha embossed on the top of it which the other does not
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@Calum It had a few small nicks, but was a whole load better looking than the other. Got it from where I bought the bike, it was the best 3mb he had, got loads of the more restrictive ones though.
Sadly no snaps NINJA, I think maybe it's a slightly older head as it had 3mb and Yamaha embossed on the top of it which the other does not
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@Calum It had a few small nicks, but was a whole load better looking than the other. Got it from where I bought the bike, it was the best 3mb he had, got loads of the more restrictive ones though.
Sadly no snaps NINJA, I think maybe it's a slightly older head as it had 3mb and Yamaha embossed on the top of it which the other does not
@Pablo13 If the other one did not have 3MB stamped on the head then it wasn't a 3MB head. Yamaha used the 3MB all the way till they discontinued the engine. I had a few non-stamped heads and run run on my dt.
The majority of power is made or lost in the head, so it is important to get it right, but I am surpised you noticed it. I would have felt you would have needed a dyno...make sure the bike is setup right. I fear something else may be amiss and might be a little expensive
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@Irongamer727 Man that's insane, it ran fine like that???
@NINJA yeah I got a bad exhaust so it's not making that much power really. It's got a whole lot of torque and I get very good gas mileage.
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It's still basically the same
Gotta be something else....not much left really, CDI, crankcase seals or clutching at straws for an extremely worn carb?
I've never inspected the reeds and the exhaust is a bit of an unknown, so could both be causing possible issues and shouldn't be overlooked.
Got a second hand CDI winging its way to me to rule that out. I'll do that and go from there....
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It's still basically the same
Gotta be something else....not much left really, CDI, crankcase seals or clutching at straws for an extremely worn carb?
I've never inspected the reeds and the exhaust is a bit of an unknown, so could both be causing possible issues and shouldn't be overlooked.
Got a second hand CDI winging its way to me to rule that out. I'll do that and go from there....
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@Pablo13 I would start simple, have you checked the plug or did you fit a new one? Perform a plug chop to see what the condition of the plug is, which will give you some clues as to what is happening.
@NINJA I've been doing plug chops but nothing untoward has been spotted, here is the most recent, was a new plug when the new piston went in
And here is the old head with no casting on top, yet the heads dome defo isnt the restrictive head
And the new fitted
I cant see anything wrong with the plug, but feel free to chime in :winking_face:
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I never said restrictive, just that it isn't a 3MB. It's odd that's for sure. I've had a few in the past, and the belgarda models are stamped P.
I think they must not be Yamaha heads or something. There must be a difference. And difference in Squish could be unnoticeable to the eye.
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I never said restrictive, just that it isn't a 3MB. It's odd that's for sure. I've had a few in the past, and the belgarda models are stamped P.
I think they must not be Yamaha heads or something. There must be a difference. And difference in Squish could be unnoticeable to the eye.
@Calum So there are other heads apart from them two, cool I didn't now :winking_face:
At least the whole top end can be ruled out now, plus ive got a spare head to play with, so not all bad. Just need to get to the bottom of this issue once and for all.
At this rate I'll have a nice stash of spares :face_with_tears_of_joy:
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@Calum So there are other heads apart from them two, cool I didn't now :winking_face:
At least the whole top end can be ruled out now, plus ive got a spare head to play with, so not all bad. Just need to get to the bottom of this issue once and for all.
At this rate I'll have a nice stash of spares :face_with_tears_of_joy:
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@Pablo13 Got 4FU heads as well, squish is noticeably different on them.
And the SP heads, which are O-Ring???
