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Front cylinder running rough (Single carburetor setup) (Connecticut)

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CoreyK250
Posts: 7
Joined: Sat Jul 16, 2022 10:26 pm
Location: Connecticut
What Virago you Own:

Re: Front cylinder running rough (Single carburetor setup) (Connecticut)

Post by CoreyK250 » Sat Jul 23, 2022 5:43 pm

Alright I tested out everything today and it all went really good bike was idling good and would Rev up... Until it got warm that front cylinder started to pop and wouldn't stay running. I'm going to go back to my single carb conversion it has the same symptoms with the daul carbs.
My next plan is to get the bike hot and do all my testing when it starts to break up again.
Thinking it can be a bad pick coil getting to hot also curious if it could be the piston rings. If it was the rings wouldn't it have a problem at idle?

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faffi
Posts: 283
Joined: Wed Jun 08, 2022 9:55 am
Location: Norge
What Virago you Own: 1982 XV750 with XV1100 engine, Seca rear wheel, XT600Z shock, Seca 650 fuel tank

Re: Front cylinder running rough (Single carburetor setup) (Connecticut)

Post by faffi » Sat Jul 23, 2022 5:55 pm

I would be very surprised if it is caused by engine wear. Maybe, but unlikely, inlet valve with no clearance. More likely something concerning spark.
The journey of a thousand miles begins with a motorcycle.

CoreyK250
Posts: 7
Joined: Sat Jul 16, 2022 10:26 pm
Location: Connecticut
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Re: Front cylinder running rough (Single carburetor setup) (Connecticut)

Post by CoreyK250 » Sun Jul 31, 2022 11:11 am

faffi wrote:
Sat Jul 23, 2022 5:55 pm
I would be very surprised if it is caused by engine wear. Maybe, but unlikely, inlet valve with no clearance. More likely something concerning spark.
Hey sorry for the late response been busy with work.
Alright so I was thinking it was engine wear as well maybe piston rings but I've replaced the front jug with a nice looking one and a different piston plus the rings. I didn't check them when I installed it just did a visual check for wear or scratches. Still had the same problem I have another camshaft so I'm going to pull this one and swap the two.
I also did a leak down test on both cylinders I preset the gauge to zero before using it. I then put each piston at top dead center hooked the gauge up and it's below 10% on both cylinders. Front 5% rear 7% I pulled the fill plug for oil and I can hear a little bit of hissing almost like it's blowing by the rings. Both cylinders are in the same range so I can't see it being exhaust or intake valve there's no hissing coming from the intake or exhaust.
I also replaced the pulse coil and no change the rear cylinder runs amazing I just don't get why the front is miss firing and dies when I do the drop test.
Any other ideas on what I should check next?

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faffi
Posts: 283
Joined: Wed Jun 08, 2022 9:55 am
Location: Norge
What Virago you Own: 1982 XV750 with XV1100 engine, Seca rear wheel, XT600Z shock, Seca 650 fuel tank

Re: Front cylinder running rough (Single carburetor setup) (Connecticut)

Post by faffi » Sun Jul 31, 2022 4:12 pm

Personally, I am where I started - that the issue is most likely with the single carb. The only confusing part is that it runs more or less the same with the stock setup. So these are the tings I would check:

Spark. Use a strobe timing light to see if spark is reliable. I know you have done much here, but that is what I would do.

Cam timing. Could it be off on one cylinder?

TCI unit. It could perhaps be bad for one cylinder only.
The journey of a thousand miles begins with a motorcycle.

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