GS650E Timing ?, Exh pressure out carbs

[Bryan22]

After re-installing the heads and cams we set the time accrording to the shop manual.... by the book. The timing mark on the crank was set to "T",
the cams were set to the correct marks chain tensioner intalled by the book. Botoom line... upon trying to start the engine we were getting exh pressure coming back out through the intake which also popped the little alum caps of the sides of the #1 and #4 carbs.

After pulling the cam cover back off and checking the timing marks,everything was still on the mark... nothing was off. Is there something we missed here? We have an actual Suzuki dealer shop manaul to go by.

What are the marks "F" and also "1-4" for on the advance gov plate? They are to the right of the "T" mark.
We did check the #4 cyl and it is TDC with the timing mark on "T"

Any help is appreciated.

Bryan & Ken

[rphillips]

I think your cams may be 180 out. Set the cam marks & timing mark as described in the manual. Turn the crank one complete turn, the "T" is at top again, see if the cam marks aren't exactly opposite of where they should be. If they are, leave the crank at this location, remove cams & reset them to spec. "T" is for top dead center, it happens twice, once on compression & once on exaust. "F" is the point before top dead center, where the ign fires

[Bryan22]

After rotating the engine all the marks still line up. This is what is very puzzling to us. Everything we have done is "by the book" and we each know a little bit about engines and so forth... so upon reassembly we double checked everything with each other and the manual... still the problem is there. Given the fact the carbs need to come off ( a real pain)for the tensioner to be removed and so on we would like to make whatever correction needs to be done so we don't have to take the carbs off again. Again, all the marks line up after rotation.

Yep, we do know that the "T" is TDC, the "F" and the "1-4" on the gov plate were not addressed in the manaul so we were curious about that.

Thanks,
Bryan

[Nessism]

On my bike I was able to get at the tensioner without removing the carbs.

Regarding the timing being 180 degrees off...welcome to the club. Same thing happened to me. I wound up removing the spark plug on cylinder #1 and looking for the piston at TDC before aligning the crank with the "T" mark.

[rphillips]

For compression to blow out the carbs, the intake valve must be open when the piston is coming up. On the compression stroke both valves should be closed. On the exaust stroke, the ex. valve should be open while the piston comes up. If the intake is too tight, the valve may stay slightly open, even on compression. When the mark at the "F" on the ign. plate aligns with the timing mark, that is the exact point when the ign fires the 1&4 cylinder.

[Bryan22]

Now, with the cam markings and timing marks being dead on even after rotation of the crank and getting exh pressure in the direction of the intake ... could this have something to do with a the advance or retard?

I am being totally straight with all of you ... the markings are dead on, but something is obviously "off" or out of whack somewhere.

This is a real challange to figure this one out, I do see/and understand that. If you need for info from us concerning this just ask.

Thanks!

[Bryan22]

Say... many times I was told that we "are off 180" on the timing and that "this happens very easily" But when we would inquire as to how this can happen (be off 180) and where specifically it is off the 180 to give us the exh pushing out the intake... we would get no specifics on any of that and where to look.
Just tonight in looking through an Chlymer manaul on the GS550 & 750 a pic was shown of the gov plate and on that it showed a "T" mark for cyl's 2-3. that is 180 from the "T" mark of cyl's 1-4. The Suzuki shop manual did not show or mention the mark for 2-3.
So, we are thinking that in looking for the "T" mark and seeing a "T" mark and setting to the "T" mark that we we could see... we set it to the wrong one, the one for the cyl's 2-3, but had no way of knowing that. We were not in the habit of cranking the motor and looking in the timing mark slot. We did know that in the process of turning the motor by hand we would look at the "T" and then watch the cam sprockets turn as well to see where they ended up. Everything always was on the mark, but it appears now that the timing mark was the wrong one. We did not know there are 2 of them.

In the next couple days we are going to try this again and hopefully working off the correct "T" and we will keep you posted on the results.