Timing and highway overheating...please help - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 20 (permalink) Old 05-30-2011, 02:58 AM Thread Starter
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Timing and highway overheating...please help

85 VN700

Just recently rebuilt motor...replaced crank, rods and cases(using parts from a 2004). I am 95% sure I timed it correctly. The bike starts up immediately idles and runs very well, no backfiring or popping. There maybe a slight decrease in power from before but it may just be my imagination as it's been 2 years since it ran. After riding 15 min especially on the highway the bike overheats.

I did everything to rework the cooling system. New radiator cap, new thermostat, distilled water w/ water wetter and bled the coolant system of all air bubbles. Also wired the radiator fan to run continuously. Bike still over heats. Then I pulled the new plugs that I had installed, all 4 are white....the bike is running lean on both cylinders.

The carbs are exactly the same as they were before the bike blew up. Same mixture screw settings, same jet kit, every thing exactly the same as before and the bike never ran lean. The carbs just sat for 2 years drained of gas off the bike in a box in my garage. So I am 99.9% its not a carb problem.

Can I be 1 tooth off on timing the cams on both cylinders retarding or advancing the timing causing the bike to run as described above(good with a loss of a little power and severely lean overheating the bike).

OR

Would any amount of being off on the timing cause the bike to run terrible or not all.

Please help this is driving me crazy I put a lot of money and time into rebuilding this motor. The bike runs really good it's just running extremely lean and overheating.
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post #2 of 20 (permalink) Old 05-30-2011, 10:08 AM
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I am no expert in this area, but I believe you would immediately notice if the timing was wrong even by one tooth.

Does the top of the radiator get hot indicating that the coolant circulates? I don't remember how the coolant hoses are routed in VN750, but often you can check if the coolant starts to circulate by removing the radiator cap and observing through the neck if anything happens when the engine heats up to normal operating temperature. Just first remove some liquid or it will overflow as it heats up.
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post #3 of 20 (permalink) Old 05-30-2011, 12:04 PM
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What jets do you have in your carbs? Honestly......to me it sounds like you have a major blockage in either your radiator or your engine block. Is your thermostat installed the correct direction? Could your radiator cap bad/weak? I honestly don't understand........With Water Wetter/Distilled Water and Fan running all the time it should be running cool.
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post #4 of 20 (permalink) Old 05-30-2011, 05:57 PM Thread Starter
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Quote:
Originally Posted by pappa View Post
I am no expert in this area, but I believe you would immediately notice if the timing was wrong even by one tooth.

Does the top of the radiator get hot indicating that the coolant circulates? I don't remember how the coolant hoses are routed in VN750, but often you can check if the coolant starts to circulate by removing the radiator cap and observing through the neck if anything happens when the engine heats up to normal operating temperature. Just first remove some liquid or it will overflow as it heats up.
Yes coolant is circulating top of radiator hotter then bottom...used laser thermometer to check.

Bike is running very lean as indicated by all 4 plugs being white....It's not the carbs as the bike running pretty good just hot because of the lean condition...the only thing i can think of is it's out of time....but how is it out of time and running really good just hot?

Last edited by ckrockets; 05-30-2011 at 06:02 PM.
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post #5 of 20 (permalink) Old 05-30-2011, 06:01 PM Thread Starter
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Originally Posted by BRET H View Post
What jets do you have in your carbs? Honestly......to me it sounds like you have a major blockage in either your radiator or your engine block. Is your thermostat installed the correct direction? Could your radiator cap bad/weak? I honestly don't understand........With Water Wetter/Distilled Water and Fan running all the time it should be running cool.
me either....on the VN there is only one way you can install the thermostat so it's good....coolant is definitely flowing through the radiator and engine block....

this is absolutely driving me crazy
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post #6 of 20 (permalink) Old 05-30-2011, 06:37 PM
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Running too lean can be a cause of overheating too. Why not enrich the mix and see if the situation improves?
Bronson.

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post #7 of 20 (permalink) Old 05-30-2011, 07:32 PM
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Quote:
Originally Posted by Bronson View Post
Running too lean can be a cause of overheating too. Why not enrich the mix and see if the situation improves?
Bronson.
X2^^^^^

Have the fuel/air mix screws been unsealed and adjusted out (richer).
That might be enough. Shouldn`t need bigger jets.

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post #8 of 20 (permalink) Old 05-30-2011, 08:32 PM
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Quote:
Originally Posted by ckrockets View Post
85 VN700

Just recently rebuilt motor...replaced crank, rods and cases(using parts from a 2004).
The first thing I can think of is that you rebuilt a 700cc motor with parts from a 750. I guess they fit or you couldn't have gotten it back together and running, but is there a chance that the timing marks are slightly different between the two? Longer rods? Slightly different spacing on the crankshaft throws? I'm asking this of everybody out there.

'03 VN750 "Rosie"
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post #9 of 20 (permalink) Old 05-30-2011, 09:06 PM Thread Starter
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Quote:
Originally Posted by bstew7890 View Post
The first thing I can think of is that you rebuilt a 700cc motor with parts from a 750. I guess they fit or you couldn't have gotten it back together and running, but is there a chance that the timing marks are slightly different between the two? Longer rods? Slightly different spacing on the crankshaft throws? I'm asking this of everybody out there.
Everything that I have read says the only difference in the 700 and 750 is the bore dia....cases, crank, and rods are all the same.
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post #10 of 20 (permalink) Old 05-30-2011, 09:20 PM Thread Starter
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Originally Posted by OlHossCanada View Post
X2^^^^^

Have the fuel/air mix screws been unsealed and adjusted out (richer).
That might be enough. Shouldn`t need bigger jets.
Yes....bike has aftermarket cobra exhaust, air pods and Factory stage 3 jet kit....bike was tuned and ran perfect before rebuild...everything is the same now the carbs in theory should need no adjustment....

The major overheating is taken place when i ride the bike on the highway....at these speeds and % throttle the carb slides are probably about 3/4 of the way up...so the main jets are supplying most of the fuel...not sure adjusting the enrichment screws will do anything....as i said the bike starts and idles near perfect...
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