Hey everyone! Just wanted to give an updated on since my partial top end rebuild on my 71 R75/5 WITH MIKUNI CARBS a few weeks ago:
I've probably ridden it about 50-85 miles since replacing rings, adjusting valve seats and the like. put eveverthing back together and seems to run fine overall. Can I get some feedback on the following observations? I am learning so any helpful insight or things to check would be appreciated. Thanks....
Couple observations:
1) On startup bike smokes a little and then stops after a minute or so upon warming up. Mostly on right side exhaust. Bike is on centerstand while not in use.
2) Today, I went for a short ride in this high heat in NC, maybe 40 miles. Bike ran fine. Stuck in a little stop and go traffic, it started puffing black smoke out exhaust while standing. Again, seemed to stop once bike was moving.
3) Did a compression test on cold engine - Left side: 135 psi, right side: 120 psi. Took the plugs out. installed compression guage and cranked engine about 4 times with electric start with throttle wide open. Is this correct?
4) here is a pic of my spark plugs, the black one is the right cylinder:
http://i1182.photobucket.com/albums/x44 ... G_4540.jpg
Should I just let bike alone and run as to allow rings to seat longer? Or should I be concerned about something? Let me know your thoughts....
Tope End Update
Tope End Update
Last edited by hudson on Sun Jun 12, 2011 4:10 pm, edited 2 times in total.
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Kurt in S.A.
- Posts: 1604
- Joined: Tue Aug 03, 2010 12:08 pm
Re: Tope End Update
3) Compression test...if the stock CV carbs, then you got low readings for compression. Holding the throttle wide open doesn't raise the slides, like they would on the slide carbs. For the CV carbs, your best bet is to quickly unbolt them from the input head rubbers or at least come in from the front of the carb and stick a soft piece of wood to hold the slide up.
Kurt in S.A.
Kurt in S.A.
Re: Tope End Update
Sorry Kurt - I meant to add that I have mikuni carbs VM on the / 5, not stock carbs. The throttle wide open would open these up I believe, right?
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Major Softie
- Posts: 8900
- Joined: Tue Aug 03, 2010 1:46 pm
Re: Tope End Update
Yes.hudson wrote:Sorry Kurt - I meant to add that I have mikuni carbs VM on the / 5, not stock carbs. The throttle wide open would open these up I believe, right?
I wouldn't worry about the compression yet. At least get a few hundred miles on it, and do some high load running. Then if it's still off start investigating. A leakdown will give you more information, as it will identify where the pressure is escaping.
MS - out
Re: Tope End Update
Ok. I was planning on riding my /5 on the blue ridge mountain trip this weekend. Wanted to make sure it would ok to do so without hurting anything. Also, I since it went through that heavy smoking scenario in stop and go traffic today, it made me wonder if everything is ok. I don't want to be stranded because I will be atleast 6 hrs from home.
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Major Softie
- Posts: 8900
- Joined: Tue Aug 03, 2010 1:46 pm
Re: Tope End Update
Besides, black smoke is usually an indicator of a rich mixture, rather than oil burning (which is usually more bluish smoke).
MS - out
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Deleted User 62
Re: Tope End Update
Hudson, the oil fouled right sparkplug is usually due to excessive blowby past the rings going out your breather and into the right carb, but in your case it might just be normal until the rings settle in. I would retorque to 25ft/lbs (oily nuts) and adjust the valves again, after a few heat cycles the head gasket will have settled in as well, closing the lash. Don't want to burn those new seats, do we?hudson wrote:Hey everyone! Just wanted to give an updated on since my partial top end rebuild on my 71 R75/5 WITH MIKUNI CARBS a few weeks ago:
I've probably ridden it about 50-85 miles since replacing rings, adjusting valve seats and the like. put eveverthing back together and seems to run fine overall. Can I get some feedback on the following observations? I am learning so any helpful insight or things to check would be appreciated. Thanks....
Couple observations:
1) On startup bike smokes a little and then stops after a minute or so upon warming up. Mostly on right side exhaust. Bike is on centerstand while not in use.
2) Today, I went for a short ride in this high heat in NC, maybe 40 miles. Bike ran fine. Stuck in a little stop and go traffic, it started puffing black smoke out exhaust while standing. Again, seemed to stop once bike was moving.
3) Did a compression test on cold engine - Left side: 135 psi, right side: 120 psi. Took the plugs out. installed compression guage and cranked engine about 4 times with electric start with throttle wide open. Is this correct?
4) here is a pic of my spark plugs, the black one is the right cylinder:
http://i1182.photobucket.com/albums/x44 ... G_4540.jpg
Should I just let bike alone and run as to allow rings to seat longer? Or should I be concerned about something? Let me know your thoughts....
Re: Tope End Update
Ok everyone. Thanks for the input. It appears on burning rich and at this point the right side has blowby past the new rings perhaps until the new rings are settled. About many miles should I drive as is before relooking into, if such symptoms persist? I will retorque & adjust valves before I leave Thursday just to be safe. Perhaps this trip will sort out the rings & oil fouled sparkplug?