 |
|
 |
|
|
| Author |
Message |
| StagHF |
This post is not being displayed .
|
StagHF
L Plate Warrior
Joined: 19 Jul 2017
Karma :  
|
 Posted: 13:34 - 19 Jul 2017  Post subject: Cam Chain rear cylinder problem |
 |
|
Hello all, New to the forums.
Have a problem with my Hyosung gt250r engine. I originally removed the engine from the bike for a faulty cam chain tensioner. Once the engine was removed i removed both of the heads to see which one of the cam chains was loose, Then removed the stater motor cover to reveal the magneto, When spinning it it spins, Then all of a sudden it sounds like it hits something, A bit of a thud and wont spin anymore, If you remove the rear cylinder cam chain tensioner, So the cam chain is loose it spins freely, As long as the rear cam chain is not spinning around if that makes sense.
So the problem must be to do with the rear cam chain ?
We have taken both heads off, The pistons are completely fine, The piston barrels are fine, No scratches or anything like that. There is no metal in the oil.
What do you guys think it could be ?
Thanks |
|
| Back to top |
  |
You must be logged in to rate posts |
|
 |
| Tankie |
This post is not being displayed .
|
Tankie
Crazy Courier
Joined: 24 Feb 2017
Karma :  
|
| Posted: 18:06 - 19 Jul 2017 Post subject: |
|
|
sounds like with a slack cam chain has jumped the sprocket, so cam timing is out and a piston and valve have touched, check for bent valve.
Your in it, up to your neck, a lack of practical knowledge is going to cause you to invest a lot more time, money and effort to rectify the original and the induced faults.
Check the valves, reassemble the engine with new gaskets set up the cam timing ,fit the tensioners, rotate the engine 2 complete turns re check the valve timing , you should be there.
____________________
Always learning, everyday is a school day |
|
| Back to top |
 |
You must be logged in to rate posts |
|
|
| StagHF |
This post is not being displayed .
|
StagHF
L Plate Warrior
Joined: 19 Jul 2017
Karma :
|
|
| Back to top |
| |
You must be logged in to rate posts |
|
|
| temeluchus |
This post is not being displayed .
|
temeluchus
World Chat Champion
Joined: 01 Oct 2008
Karma : 
|
|
| Back to top |
 |
You must be logged in to rate posts |
|
|
| Stag |
This post is not being displayed .
|
Stag
L Plate Warrior
Joined: 26 Mar 2017
Karma : 
|
|
| Back to top |
| |
You must be logged in to rate posts |
|
|
| Teflon-Mike |
This post is not being displayed .
|
Teflon-Mike
tl;dr
Joined: 01 Jun 2010
Karma : 
|
| Posted: 14:46 - 20 Jul 2017 Post subject: Re: Cam Chain rear cylinder problem |
|
|
Do you have a workshop manual?
It's not the most common bike about, so probably not going to find many that have intimate knowledge of its innards.
| StagHF wrote: | I originally removed the engine from the bike for a faulty cam chain tensioner. |
Oh-Kay...on what basis was that diagnosed?
Has it got a manual CCT or a hydraulic?
If manual, why was first course to pull the motor and start stripping; why not adjust manual CCT?
If Hydraulic; likelwise; why frst course to start pulling engine to bits; why not do oil change and flush, or if that o effect, remove and de-gum CCT plunger(s)
| StagHF wrote: | Once the engine was removed i removed both of the heads to see which one of the cam chains was loose, |
Err... its an over-head-cam engine... if you took both heads off, I would sort of expect BOTH cam-chains to be very loose.. as in hanging over the barrel...as you'd have to remove the cam from the head to take the head off!
Do you mean rocker covers.. that's what I would remove to inspact the cam-chain!
| StagHF wrote: | Then removed the stater motor cover to reveal the magneto |
Err.. again... remove starter motor cover.. I'd be a bit surprised to find a magneto in there.. bit like taking the lid off the coffee jar and finding sugar.... (though that probably wouldn't be much of a surprise in this house lol)
Mag, starter cam-chain.. what sort of generator do you have? Is it on the end of the crank, or is it a piggy-back unit, with its own chain drive? If so, and common issue with my CB Seven-Fifty, the alternator chain goes slack, and rattles like a cam-chain.. hence query how you diagnosed slack cam-chain... as in was it a CAM chain? OR an alternator chain, or a starter chain?
Starter; again, what sort of starter engagement do you have? Some small bikes like the Honda benleys have a chain driven starter, with a one-way roller, that if the roller doesn't dissegage, can make the chain rattle. I would suspect you more likely have an idler clutch, a gear between the starter and the crank 'chucked' into engagement when the starter turns and chucked out of engagement when the crank starts spinning quicker.. these may be on either side of the engine, in the primary drive side or the magneto side (if eoc mag).
Slightly hazy description of symptoms, does 'might' fit with a slipped, worn or miss-assembled starter clutch.. but not with...
| StagHF wrote: | If you remove the rear cylinder cam chain tensioner, So the cam chain is loose it spins freely, As long as the rear cam chain is not spinning around if that makes sense. |
Not really.. if I removed the cam-chain tensioner, I would expect the chain to rattle, but provided it didn't snag or jump the cog, it to make not a lot of odds to very much at all.
If the rear cam-chan isn't turning?!?!?!?  I'd not extect t to make two full crank revs before the piston struck an open valve.. if t didn't, I'd consider myself rather lucky that the cam was by pure serendipity in the 120 deg of cam rotation that held the valves shut during the compression and power stroke aprox 3:1 odds against, and I'm never that lucky!
Bottom line:-
IF you have assembled correctly, to the book, from scratch, and checked and double checked as you have gone, and fixd the cam-chain 'problem' then your original problem should be solved...
If not.. you likely haven't fixed the original problem.. so was the diagnosis correct? OR you have effed up in something you have done; back track, and check, and re-do.
Does sound like a starter clutch cock-up; but more likely, that you haven't fixed cam-chains & tensioners properly, IF loosing one makes difference you suggest.. re-vsit.. undo what you done; double check, tripple check, re-do to the book.
Mucking about wth CCT's I would pay close attension to the tensioner blades, and the front run 'slipper' which likely are dislodged and may put a spanner in the works if loose; not payng attention on re-assembly to little lugs and pips and things as to how they fit, especially if working blind in restrictive gallery, trying to fix with least disturbance, rather than biting the bullet and doing job from the bottom up, as they would in the factory building from scratch.
____________________
My Webby'Tef's-tQ, loads of stuff about my bikes, my Land-Rovers, and the stuff I do with them!
Current Bikes:'Honda VF1000F' ;'CB750F2N' ;'CB125TD ( 6 3 of em!)'; 'Montesa Cota 248'. Learner FAQ's:= 'U want to Ride a Motorbike! Where Do U start?' |
|
| Back to top |
| |
You must be logged in to rate posts |
|
 |
Old Thread Alert!
The last post was made 6 years, 274 days ago. Instead of replying here, would creating a new thread be more useful? |
 |
|
|
This page may contain affiliate links, which means we may earn a small commission if a visitor clicks through and makes a purchase. By clicking on an affiliate link, you accept that third-party cookies will be set.
|
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You cannot download files in this forum
|
Read the Terms of Use! - Powered by phpBB © phpBB Group
Debug Mode: ON - Server: birks (www) - Page Generation Time: 0.07 Sec - Server Load: 0.42 - MySQL Queries: 17 - Page Size: 56.38 Kb
|
Help & FAQs
Search BCF
Members
Groups
Events Calendar
rating
rating