engine smokes on start up

[RAYZ1]

flipped the rings over and hey presto perfect, once married into the honed bores after a hundred miles not a whiff of smoke, unless it sits over the winter and you get the startup puff, then clear

Usually more prominent when left on side stand - sit it up on centre stand may help .... valve guide seals (again)?

Could be , but I have noticed it's now decreased to a very small amount on 1st start after months , the seals and head were done by kip kawa,

[corky]

Hi Ray should have been more specific, rings 1 & 2 were in the wrong position on 3 of the pistons, 1 was correct. I cannot understand how someone who is supposedly an expert can strip an engine completely, vapour blast it and then reassemble it without replacing worn parts or putting things back correctly. The rest of the bike is perfect. Done by 2 different people

[RAYZ1]

To many people fail to RTFM, especially experts.

If after a decent run and the bike is running tops then it's not likely to be rings.

If you still find it smoke or oily and compression is down then probably still rings / bores

Although check shims for clearance to ensure valves shut when hot

It's very frustrating as I know what I'm going through with my gs750 with low compression issue, no smoke, no popping or any other symptoms so have stripped top end right down and going through it systematically

[frizzy]

thanks again guys for all the useful tips, I'm going to take it out for a hard blast when the weather is in my favour and see if it sorts itself out but if not ill whip the head and block off and check all those. cheers frizzy

[Taffus]

Anecdotally, I bought a 900A4 earlier this year which had stood for 9 years.
The bike had been well looked after, initial running for the first 500 miles I had plug fouling on pot 4, which meant I had to replace that plug each time as it had been fouled so bad.

Now after miles with no changes, the bike flies, no more fouling, good spread of power and starts first time every time.
So I would suggest you ride it, I try to ride mine daily as I really enjoy it (though I still hate polishing) there were other niggles but they have gone due to use

[johny brando]

Hi Ray should have been more specific, rings 1 & 2 were in the wrong position on 3 of the pistons, 1 was correct. I cannot understand how someone who is supposedly an expert can strip an engine completely, vapour blast it and then reassemble it without replacing worn parts or putting things back correctly. The rest of the bike is perfect. Done by 2 different people

Rays right & none of us wanna be the Grim Reaper here but just working as a mechanic at a bike shop mean JACK S ! Unfortunately the people that write Shop manuals make stuff up's too ....i.e. Middle ring- Tangential being shown fitted upside down in some manuals....this doesn't help the cause aye ! This said for the # 1 and #2 rings to be misplaced on 3 of the 4 Pistons & re-ringing without a light hone ....Mmmm you'd have to throw a large Question mark over every thing this bloke has touched ! I personally would have been taking all valves out as who know's what else might now lay there ...springs worn or upside down ?,valve seals secure & not had lips nipped ? , seats cut too wide or narrow ?, guides reamed correctly ? the list goes on . If it's all back together again now & running OK , well best Enjoy & just continue riding it & see what / or if anything happens.... but at the first sniff of anything .Stop it & prepare to maybe tear it down & check everything carefully. Just like John Wayne always did....It,s best to head the trouble off at the pass ! haha. Good luck Bud. Johny B

[RAYZ1]

oil control spring overlapped or the ends have broken check the part of the rings that are coloured yellow & pink in this photo

Remember fit the gold corrugated part first then the 2 snap rings . They generally have a tiny lip at the back which the snap rings push against

[RAYZ1]

to share my recent top end build "problems"

Just finished rebuilding the top end of my gs750 a copy of the z1 engine ( same bore, valve size, and valve timing) . Some points . I had new rings in , but the bores were not honed, they were glazed.

I made the unforgivable mistake of assuming this was the cause of the low compression , or I had the rings turned wrong way up - easy done even if you concentrating not to , a moments distraction and you can turn one over in your hand with out realising

After fitting new rings, I set up the shims with the head on the bench, I set clearances anything .1 to .13.

On engine assembly , rechecked compression, down on 2 pots??. Checked shims in situ on assembled engine. 4 had tightened right up, dropped them a further .05 and he presto compression back up on all 4

I found I wasn't happy about shimming on the bench as you bolt the cam down it will rotate ever so slightly as it rides the cam of the valve being depressed ( you area checking the others !) so you don't get optimum position and you cant turn the cam back to where it should be . The lift on the cam starts a lot earlier than you might think

Anyway bike engine now as it should be, rapid, rips past the ton

- to be honest I think it was shims all the time , so if you have low compression - check clearances first , anyway bores will be better now they have had a hone with new rings - motor only had 6k on it, the previous owner never thrashed it - hence the glazing

The top end has been repainted, triple checked and no weeps, plenty valve clearance

Morale is check the easy and serviceable items first its all to easy to assume there is a major problem, tight shims will screw up your performance big time

[Pigford]

I found I wasn't happy about shimming on the bench as you bolt the cam down it will rotate ever so slightly as it rides the cam of the valve being depressed ( you area checking the others !) so you don't get optimum position and you cant turn the cam back to where it should be . The lift on the cam starts a lot earlier than you might think

We had this discussion a while back - and I got slated for suggesting "bench setting of head & shims could introduce a variable into the equation".

In theory it should be fine - but in practice I've heard this tale a couple of times now

[johny brando]

I found I wasn't happy about shimming on the bench as you bolt the cam down it will rotate ever so slightly as it rides the cam of the valve being depressed ( you area checking the others !) so you don't get optimum position and you cant turn the cam back to where it should be . The lift on the cam starts a lot earlier than you might think

We had this discussion a while back - and I got slated for suggesting "bench setting of head & shims could introduce a variable into the equation".

In theory it should be fine - but in practice I've heard this tale a couple of times now

Shimmed Heads on bench countless times..."easy with valves in " never had a problem !! ONLY EVER One Cam at a time & using 2 x 10mm spanners on the Cam bolts & only ever turning the Cam clockwise ...or you may un-wittingly slacken them bolts from there Loctited 12 Lb / Ft Torque!!!! ( first ensure the Head is sitting on 2 Flat blocks of wood about 1 or 2 inches high...one each side of the head ..this to stop the opened valve contacting the face of your Bench & bending them ! & Always ensure you pull the Cams down in an even & Level plane ! I find the cams always stop where I want em to without a problem but should you have a problem well you could always stop them were you want with the Spanners to take your measurement ..... this always taken at the Heel of the Cam with the Lobe pointing directly away from the buckets directional plane aye !!! If you have a reasonable shim collection like me ..... well , I actually tend to normally do it with NO springs fitted at all, just the Buckets in their corresponding homes ....just put all undersize shims in your buckets ...Cams & buckets lubed & back in & nip up the cap bolts only !!!! Doing this now just one valve at a time, slide the correct valve back into it's corrosponding Guide & using one Finger from below just hold the valve closed against it's valve seat while with your other hand you measure your clearance using your Feeler gauges..... measure & note the massive valve clearance that you will now invarably have..... this due to the undersize temporary shim your using & then you just quickly work out using the clearance that you just got and the temporary shim size, what size shim you actually need allowing & factoring in your desired clearance for that Camshaft installed i.e.( inlet or Exhaust )...... now supporting the valve head with your finger just let the valve drop a little....just enough to be able to swap out the shim for the now correct one . Now move onto the next valve & do the same ...theres No need to remove the cam until all 4 valves are shimmed correctly (don't mix anything up now mark all & keep them in order ) Jobs a good n. Hope I made sense there ! Cheers, Johny B