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Top end question

Old 07-25-2005, 12:28 PM
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Top end question

Hate to admit it, but I screwed up my top end last summer when on a trip the CCT went kaput. I replaced the valves and guide seals, but not the guides (Why, you ask? I guess cause I'm just dumb .

Anyway, looks like I'm getting some oil leakage there and I'm looking at another rebuild. Questions for you experienced gear heads out there: Should I rebuild what I've got (replacement part running around $400) or buy some used heads and simply bolt them on (costing around $150)?
If I go the rebuild route, can I just replace the guides or should the valves also be replaced (keep in mind the valves have about 8K on them). Same question for the guide seals - should they be replaced too, even though they are relatively new?

Thanks for the input.
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Old 07-25-2005, 02:10 PM
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Re: Top end question

Unfortunately I can't answer your question but may I suggest having the ports cleaned up while you have the heads off. I would imagine it would be worth a few hp.
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Old 07-25-2005, 02:30 PM
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You always replace the seals. You measure the guide bores to determine whether to replace them. Valves are replaced when they are burnt, cracked or can't be refaced.

Do you mean there is oil draining into the cylinders?
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Old 07-25-2005, 03:33 PM
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Originally Posted by jschmidt";p=&quot View Post
You always replace the seals. You measure the guide bores to determine whether to replace them. Valves are replaced when they are burnt, cracked or can't be refaced.

Do you mean there is oil draining into the cylinders?
Yes, I'm going through about 1 qrt every 1500 miles.

This past weekend I was on a group ride and the rider behind me mentioned he saw smoke when I was downshifting, an indication that oil was getting in via the guides (as opposed to the rings).

I don't know about his assessment, but it makes sense to me since I did top end work last year. (I figure I should have replaced the guides. No, I didn't measure them, both because I didn't think of it and because I was in a bit of a predicament.)

On the other hand, the motor has about 41k on it - any possiblitiy that the cylinders are out-of-round? My next step was going to be checking the compression.

Thanks
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Old 07-25-2005, 04:25 PM
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That oil usage would be considered normal by Honda.

I don't know of much experience with higher mileage VTRs, but it could be any of the ideas you've had.

A compression check will answer your question about rings, but not if just the oil-control side rail is bad. The idea that oil on downshifting indicates guide seals is not correct.

Top end oil drip shows as blue smoke on startup (since the oil has had all night to leak down.) Blue smoke while running could be either but is more probably rings.

BTW, to measure the guides, you'll use ball gauges and a micrometer. Neither is too expensive. To measure cylinder round you'll need the proper bore guage. Its usually a more expensive tool. Wall damage will be obvious.
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Old 07-25-2005, 04:26 PM
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Oh, and I'm sure I don't need to mention it, but overfilling could cause your symptoms too.
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Old 07-25-2005, 04:43 PM
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Re: Top end question

Thanks
Yeah, unfortunately it's not due to overfilling.
I'm surprised Honda would consider losing a qrt at that rate to be "normal."

I'm not sure about the downshifting symptom. Maybe it's more of a deceleration thing? I'm wondering if it could be smoking then because the throttle is closed but the pistons are creating a vacumm which ends up drawing oil down through the guides??

I'd really rather not have tear the engine down to do a cylinder job - please say it ain't that. Your analysis about smoke at start-up is right, though.
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Old 07-25-2005, 05:34 PM
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Thanks for the thorough reply rc996.

Although I didn't re-cut the valve seats, I did lap the seats using lapping compound and gingerly spinning the valve with a drill.

Yeah, the valves and seats were pitted (that was at about 32K). I figured it was due to a dirty air filter making for a rich mix.
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Old 07-27-2005, 04:52 PM
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Re: Top end question

Are these guys good or what? 8)
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Old 07-28-2005, 10:34 AM
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Re: Top end question

gadjet ,

I bought a new 2003 SuperHawk in late 2004 . I put 580 easy miles on it then pulled it out and put a race motor in the bike .

It's complete from starter to airbox and guaranteed perfect .

You cannot rebuild your engine for the $950.00 I'll take for this one . If interested , give me a PM .
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Old 07-28-2005, 10:46 AM
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Originally Posted by rc996";p=&quot View Post
Not good. Just curious and obsessed.
A lifetime student.
Speak for yourself. I'm spectacular! :wink:
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