Anyone ever heard of a Roadie (1600 cc) having low compression on the front cylinder and not the rear ?

Here's the back story - Dad has a 1600 ('01 I think) and when he took it in to his local shop for a fall oil change and basic inspection they told him his front compression was 120 compared to 160 for the rear. Front plug was also heavily fouled apparently. They're wanting to drop the motor and pull the front head/cylinder off.

I have an '05 and am pretty good with the mechanical side of things so it struck me a bit odd that the issues were in the front cylinder only, esp. with a common carb. I would have thought most issues would turn up in the (hotter) rear cylinder first.

One thing I did wonder about is whether they knew about the decompression device before they tested, so they are going to retest with it disconnected (although they are doubtful it would make such a difference).

He's got a dealer rejetted stock carb, dyna box, V&H Propipe, and a basic K&N. Bike has 60000 km (about 40000 mi) on it. When he moved from here (elev. 3000 ft-ish) to the coast he had the local Yammy dealer rejet to suit, and that was years ago.

If he lived near me I'd get the bike in my garage and have a good hard look, but he's 2000 km away on Vancouver Island and he's not very mechanical so there's not much chance of diagnosing it over the phone.

Ideas ?

Was there a problem with performance? If not pick the bike up from the dealer and never bring it back to them. Do all your own oil changes from now on and put a set of plugs in it if it needs them. Then smile every time you drive past that dealer. Also tell him to sign up here and he will get any help he needs to keep that bike running good.

Sounds like SVS in the front cylinder. Not typical, but I would:

1) Fill gas tank and pour in a full bottle of Sea Foam.

2) Get her up to operating temp and spray Deep Creep into carb for 30 sec. 3 times while running. The last time stalling engine with spray.

3) Remove exhaust from heads and spray Deep Creep high onto exhaust valve stems and stuff w/ rags to keep from running out onto engine. Let sit for a day or two.

4) Re-install exhaust and ride her like she was stolen hitting the limiter when hot.

5) After tank is used up, change oil (4 quarts only) and check compression yourself.

Now before you do all this you could check the valve lash on the front head first, but that spark plug would clue me that there is a lot of carbon in there.

Keep some Sea Foam available and throw in 1 Oz per tank of gas.

Ray

Decompression Solenoid does matter but doesn't nee to be disconnected. Just pull a plug from each cylinder and pull all spark plug wires. Turn the throttle full wide open and crank the engine several times to get the highest reading. My SVS treatment that Rayjay mentioned is available for download on the second page of my site along with other things.

It has been my experience that Cylinder #2 (Front Cylinder) is the one that is most affected by being either too lean or too rich (I don't think there is much difference between the 1600 & 1700 motor)I would dang sure get that bike away from the dealer like previously stated and check it out yourself. They are not only doing a ream job on the bike but your Dad as well. Compression tolerance should be 75% of the highest reading. So if the #1 was reading 160 then the lowest you would want the #2 is 120 which is what you stated. I think it is just gummed up and needs to be cleaned up....My .02 worth

I would start with picking it up and running the snot out of it, bouncing it off the limiter often, with about 4 ounces of marvel mystery oil in a tank of fuel. If it still has black front plugs after that, SVS treatment, but absolutely get it out of that shop!