Serious help/advice needed

Ok,if some of you remember i was told my sv needed new pistons and rings when she has only done 28k miles and i HADNT found any probs with her running, took her to another garage, told them what i had been told.
Now the 2nd garage have said as shes backfiring its a trapped valve, which im more than happy with cause i can live with that! oh and the rattle the 1st garage said was my cam chains was actually my cam chain tensioner!

Now 1st garage is where i work, and i had a big bust up with the boss today as he reckons im talking cr*p and IT IS the pistons etc that are shot-he wont listen to me, ive explained that she runs fine etc and he just generally made me feel very stupid and small

Know can someone please correct me if im wrong but surely if pistons/rings were shot she'd smoke? (which she DOES NOT!)
If it was a trapped valve-she'd backfire (which she DOES!)

All this is based on a compression test and leakdown test/wet test that the first garage did! (even though i had NO complaints about how she was running so why compression test?)
Any advice much appreciated.

Laura (paws)

Sounds like if there's no excessive smoke and your not using lots of oil then I'd go with the Trapped valve you could always get a 3rd opinion if you still uncertain!! The trapped valve might just want re seating/grinding not to big of a job!!!I'm sure some one more knowledgeable will come a long and give there opinion.

Hi

Just a thought, have you checked the valve clearances. They tend to get tight on the SV as the engine wears. If left too long it can end up with the valve not closing properly so effecting compression.

The rings on most modern car engines will last for up to 200,000 miles if the engine is looked after. As a bike revs higher they will tend to wear out quicker but they should be good for getting on towards 100,000 miles.

Has the bike ever been run low on oil. This can have a significant impact on the life of the rings. In many engines the cylinder bores only get lubricated by oil splashing up from the crankshaft as it rotates through the pool of oil in the sump. Low oil means no splash.

Kind regards
Tim

[rictus01]

Hi Laura,

I'm prosuming you have standard rings/pistons & bores ? and not something over sized ?

also you don't say if this is a new problem or something the bike has been suffering from for a time ?

I've worked on about 30 SV lumps and never see one with worn rings to the extent the garage was talking about, and there are many reasons for low compression, although as stated above valve clearances should have already been checked at your mileage.

"Trapped valve" and what is that then? are you talking about a valve not seating properly? which could be down to clearance or being bent, the clearance issue is easy to check, if it's bend then the question is to ask why that would be.

As to lapping in the valves, generally new engines don't require this as the seats are hardened..

So to clarify,

28k won't normally see a cam chain go, but the SV's tensioner are a known weakness, reset it and it should be fine (do this first as it may effect the stuff below / about 20 minute job)

As to the piston problem,
are you suffering any performance issues or high oil consumption ? these could point to problems. you will also have higher crankcase pressure as combustion will leak through. if not then it isn't you rings/piston causing the problem.

I'd first check the valve clearances (do a search/ perhaps an hour at most with basic tools), colour of the plugs (this will tell you if the bike is running rich (causes backfiring) or not), then airfilter (this will lead to rich running if blocked), then check the crankcase pressure.

as the rocker covers can be removed with the engine in the bike all the above shouldn't take more than an afternoon and have a minimal expense, but could save you a fair amount.

Cheers Mark.

[Sid Squid]

We need some clarification of what 'trapped valve' means, as Mark says it could mean a couple of things of which one is simply adjustment, the other slightly more serious.

Bottom line is of course the oil consumption, if this hasn't been a problem/increased then bores/pistons/rings are unlikely to be trouble.

Have the valve clearances checked. I think your right about the first garage - they sound like they are talking ********. If its not smoking (and/or there's none of that acrid smell that accompanies burnt oil) and its not using excessive oil, then I'd say your pistons and rings are fine.

Steer clear of garage Number 1, they sound like a bunch of cowboys

Matt

P.S. this spell checker is cool!

Awwwww i sooo love you guys!

Valve clearances HADNT been done at first garage when they did compression test.
Have standard piston/bore sizes.
Sorry for the trapped valve thing (im not v techically minded! ) its what the 2nd garage said-"Thats a valve prob, nothing serious, itl just mean she'll backfire"
Doesnt eat lots of oil at all.

New tensioner in=no rattle

[rictus01]

get the valve clearance done and check the timing, that should sort it then, sounds like you've got a tight one stopping the valve closing properly (will cause backfires) in order for this to be done the cams will need removing so your timing should be reset anyway .

Cheers Mark.

Originally Posted by Paws

.....its what the 2nd garage said-"Thats a valve prob, nothing serious, itl just mean she'll backfire"

I would have doubts about the 2nd garage as well - it is not serious in the sense that it can be easily fixed if spotted soon enough, but if left it will eat the valve and result in expensive head work.....

Originally Posted by rictus01

get the valve clearance done and check the timing, that should sort it then, sounds like you've got a tight one stopping the valve closing properly (will cause backfires) in order for this to be done the cams will need removing so your timing should be reset anyway .

Cheers Mark.

Cams etc have been done by the 2nd garge, i DO trust these guys, word of mouth round here is a v powerful thing
I do know of a 3rd garage/mate that i trust, 3rd opinion time?