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XR440 top end build start issues.


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So I blew the head gasket on my 97 re-bore a month ago and have been running with a silicone seal since while rebuilding a ttr250 raid as a back up. Then a week ago, cleaning my carb, I cracked off the main jet connection, was held in place by a 3-4mm of material - the rest was already broken. Glued that back together with jb weld while rebuilding the entire top end with a Wiseco kit. Have a bsr42 on the way but in the meantime am trying to start the rebuild with the patched carb because...well, I rebuilt it and I want it to work.

So, when I kick, either full or no choke, the bike spits, turns over and dies a quick death. Any opening of the throttle and it dies quicker. Before the blown gasket, I was running 155/55 jetting and getting a 1-2 kick start. Previous jetting was 145/50 and could take 5min to start the bike. I started at 165/65 and worked my way down. The plug was getting more and more fouled with oil though now I know it's from the blown gaskets.

Checked the timing on my rebuild after redoing it again and it's a half-tooth off. From what I read on the forum here, that doesn't seem like such a big deal. Doesn't it matter more if it's retarded or advanced?

Now the big question is do I continue trying to tune the patched stock carb/fresh rebuild or wait for the bsr and tune that?

Any ideas appreciated - thanks!

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I agree with Mich.

 

Yeah, you'd think bigger bore, richer jetting, but not so. After my 440 build, I stayed with the same jetting I had when it was stock bore, which was 155/55 at 3600'.

 

You'd probably be better off just waiting for the BSR to come in. Being impatient can cause you to overlook things.

 

When the crank is positioned at TDC and you hold the cam sprocket with its marks level with the head while pulling the front side of the cam chain taut and wrapping it over the cam sprocket, if then, the sprocket marks seem off with the head, it has to do with chain length/wear stretch. Nothing you can do but replace the chain.

 

Given chain wear, the normal "off" position of the cam sprocket would be with the "rear" sprocket mark dipped below the head.

Edited by Trailryder42
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Yes, originally, it was jetted 145/55 though a beast to start so I eventually found 155/55.

Yeah, think I will wait - Im frustrated hearing it almost start - and it sounds like the carb issues I've had in the past but the lack of start may be from the recent carb break and repair which would really throw a wildcard in there.

Thanks for the info on the timing chain - I figured that it is a bit stretched. I'll pop open the top cover today and check to make sure it's rocked back like you described.

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An update. My friend spent all afternoon cleaning and overhauling at bsr42 I bought off ebay. It wasn't an original - Chinese clone - and filthy internally. We put it on and got the same response as with the broken and repaired stock carb.

Time to tear the head apart again and see where we went wrong?

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