1978 Suzuki GS750 EC Mikuni VM26SS Part#

[nickr234]

ahhh yes i did say that didn't I

i didn't remember saying that i was thinking about replacing the cylinders. lol anyways. yes i am because when this bike was sitting in my dad's garage for about 19 years and at some point the engine decided to seize up.

i put mavel mystery oil down into the plug holes and let it set for a week. that fixed it thankfully but at somepoint im sure the commpression related to cylinder heads probably suffered. i did a leakdown test so see where compression was being lost and it didn't sound like there was any leaking into the crankcase but im worried about it.

but there was alot of compression being lost from the valves. about 10-15 percent on cylinder 1,2, 4, and about 20-25 percent on 3. so there is no question my vavles need to be shimed.

and maybe if some of the rings and cylinders heads need to be replaced it is on 3 since that seem to have the most compression lost.

Thanks everyone for your insight.


:EDIT also since my breather tube no longer will have anything to go into should i plug it up? Or will that hurt the engine? EDIT:

[hampshirehog]

You can leave the breather tubes off but don't leave the vaccuum one off (or at least blocked if you're running a non-standard fuel tap).

You get no advantage at high throttle openings by not synching. You synch at low slide opening to get a smooth slow run and transgression - at low throttle openings the disparity between slide heights shows up much more as a percentag of throttle opening. At WOT if you've done a good bench synch the percentage differences are insignificant.

I've been looking at another way of synching carbs without using the gauges and I've now tried it on a dozen different sets of Mikunis. Measure (using calipers) from the top of the carb to the top of the slide on each carb (same point on each carb). I've followed up with the vaccuum gauges and not needed to adjust anything. I was surprised at how accurately Mikuni manufactured their carbs and slides. I'm not sure if this will hold for all carbs as it's still only a small trial but it looks promising. Of course you can only use it on carbs where the vaccuum levels should be equal - there would be a bit of guesswork on those carbs where the outers are meant to have 'half a ball' more.

Do your valve clearances then ride the snot out of the bike. Check your compression figures again after a good few miles - could make all the difference if she's been stood.