SV650.org - SV650 & Gladius 650 Forum



Bikes - Talk & Issues Newsworthy and topical general biking and bike related issues. No crapola!
Need Help: Try Searching before posting

Reply
 
Thread Tools
Old 18-05-24, 07:01 AM   #1
Seeker
Member
Mega Poster
 
Seeker's Avatar
 
Join Date: Jun 2016
Location: NE Lincs
Posts: 1,082
Default tighter or looser?

There are some topics that I have stored in my brain that I carry along with me confident in the veracity of my thoughts. Then I verbalise them to someone and my firmly entrenched foundations are shaken.

Valve clearances - do they tighten or loosen with mileage?

I always thought they tightened as the valve seat wears. My MT07 friend contradicted this and claimed the dealer said they would get noisy if they needed reshimming.

Googling it gives mostly (but not completely) that they tighten.
__________________
2016 SV650AL7
2023 GSX-8S
Seeker is offline   Reply With Quote
Old 18-05-24, 08:51 AM   #2
Sir Trev
Member
Mega Poster
 
Sir Trev's Avatar
 
Join Date: Jun 2005
Location: High Wycombe, where the chair factories used to be
Posts: 1,449
Default Re: tighter or looser?

I'm with you on tightening. The Mundaneo I had with a LPG conversion did not have the lubrication unit fitted and all my clearances tightened due to valve recession. The garage lightly ground something or other, so they did not have to take the head off, and it ran WAY better afterwards.
__________________
We are the Goon Squad and we're coming to town, BEEP BEEP!
Sir Trev is offline   Reply With Quote
Old 18-05-24, 10:10 AM   #3
glang
Member
 
Join Date: Oct 2007
Posts: 544
Default Re: tighter or looser?

I think the confusion is because both can happen in different cases. If theres valve recession then they will get tighter but if not and you do a lot of high revving miles the shim can get a wear spot in it where it sits on the valve stem plus the cam/bucket themselves wear all of which increase the gap...
glang is offline   Reply With Quote
Old 18-05-24, 11:51 AM   #4
Craig380
Member
Mega Poster
 
Join Date: May 2015
Posts: 1,245
Default Re: tighter or looser?

Quote:
Originally Posted by glang View Post
I think the confusion is because both can happen in different cases. If theres valve recession then they will get tighter but if not and you do a lot of high revving miles the shim can get a wear spot in it where it sits on the valve stem plus the cam/bucket themselves wear all of which increase the gap...
Exactly this. Regular high rpm usage will accelerate valve seat recession (thus clearances closing up) simply because the valves are slamming more frequently into the valve seats per hour of riding.

However, if the cam lobe's opening angle is aggressive, or the contact area between cam and bucket / follower is relatively small, you get cam / follower wear which opens up the clearances. This was a problem with Honda's early VF750 with the 'chocolate cams' fiasco, the cam opening angles were very steep and the friction forces this placed on the cam lobes & followers broke through the oil film on the mating surfaces, causing very rapid wear and in some cases, written-off engines.
Craig380 is offline   Reply With Quote
Reply

Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Crash.NET - Lowes: Shoulder stronger, Moto2 tighter than ever NewsBot News 0 01-04-20 06:10 AM


All times are GMT. The time now is 11:46 AM.


Powered by vBulletin® - Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.