82 yamaha seca - high rpm misfire

[ZaGhost]

Carb sync can do that, I did a bench sync last time I had them off, could be the root of my problem as well. Right now the left side is running a bit rich. I also need to replace that vacuum line, it's old and in rough shape.

My voltage reg is toast so that may be part of it as well for now, I'm getting no charge to the battery so I'm thinking it could just be lack of juice at higher RPM's. Getting a replacement later this week, will see if that's it.

These old girls pickup a lot of electrical issues after they sit.
Have you replaced your fuse box yet? That can be a HUGE!!! weak point in the system. I replaced mine (was corroded pretty bad) with inline weatherproof blade fuse holders.

But that big of a difference between caps is an issue for sure.

[ZaGhost]

Just clicked on the link in the first post.
WOW, that thing is in great shape!!!!
Mine had a missing panel, and was half apart when I got it.

[ZaGhost]

Well, guess what? hehehehehe

Pulled the carbs today... found my left main jet in the fuel bowl.
AND!!!! my left and right jets were also swapped, I did mine 1 at a time so I couldn't mix them up, meaning a PO had done it, and lived with it. ACK
While I was in there I did a clunk test on the Needle pistons, cleaned the bores with some 1000 grit we sandpaper and wd-40 to be sure there was no resistance.

Runs MUCH better now, wow....

Anyways, Here's a few quick pics I did up, will be making a dedicated page now I think.
http://zagnet.dyndns.org:8080/Maxim/

[magna85]

1985 magna 6000 rpm hesitation

Have just been reading the post about your 82 yamaha.

I have a 1985 honda magna (california edition), V30, 500cc V4.

As I open the throttle it accelerates smoothly until 6000rpm. At this point it pulls very jerkily and misfires etc. If I hold the throttle open for a few seconds if finally pulls through this stage, and revs smoothly up to the red line.

Because of this problem I have just removed the carburettors and thoroughly cleaned them. But this hasn't fixed the problem.

Having read your post it sounds like you had the same problem.
So in your opinion, having read my confusing post what do you think is wrong with my bike.

Look forward to hearing from you

Many Thanks

Tom

[ZaGhost]

I'd say, clean the carbs yet again, likely something is still clogged.
I have an old Handa scooter as well, had to clean the carb 3 times to get it really clean...

[magna85]

Thanks for your speedy respose and advice.

It is quite possible that I didn't clean the carbs thoroughly enough and I will look into it right away..

However If my carbs are not synchronized properly what would be likely effect upon my bikes performance; Could the temporary pause in the acceleration at 6000 rpm be explained by un-synchronized carbs??

Thanks very much for your help with this problem

Tom

[ZaGhost]

Could be something that simple.
Did you bench sync them when you cleaned them?
If not try that. I did mine so when I looked through the hole at the butterfly valve I could see just a small crack of light, then adjusted the sync on carb 2 to match

You have a bit more work to do with 4 carbs, but an eyeball sync should put you close. Then you can fine tune it with a manometer (commercial or home made)

[NorthernPete]

thats a very sharp lookin XS.....mine was...ermmm.... well, click and see for yourself..... I sorta almost miss the sparkplug eating machine...