My Bike's Overheating, Why? (sorry for the honda question)

truthfriend7 · 02-15-2009, 07:05 AM

Let me apologize for asking a question about a non-china bike. I just feel more comfortable asking you guys (being a former china biker myself) and the bikes is a similar design. It's a honda xl600 single cylinder, air-cooled engine with overhead valves. I recently had it bored out with a new piston and lapped the valves.

It runs and drives okay, but the spark plug looks too hot. Also I'm only getting about 20 miles-per-gallon. My understanding is that I should be getting twice that. So it must not be a fuel mixture issue because I'm burning through the gas. There's no fuel leaks I can see. I checked the timing and it's perfect. I did notice that one of the intake valves was too tight on the clearance but that's it. Do you think that's what was causing this or something else?

Thanks for your help, and don't feel like you need to waste any time looking for an answer. Just if any of you mechanics have something off the top of your head that helps I appreciate it.

TeamCheap · 02-15-2009, 07:56 AM

Who did the reassembly ?

VinceDrake · 02-15-2009, 09:46 AM

If it's really recent, the engine could just be that tight. (i.e. between the rings and the bore)

A rebuilt engine creates a pile of heat for the first few hundred miles, until things are mated correctly, and more fluid. Also, all that extra friction does destroy fuel mileage.

Personally, on a fresh 4 stroke motor-cycle engine I like to throw some 2 stroke oil in the fuel, and a bottle of EOS (A ZDDP additive) just to try to soothe the hot spots, until things get broken in some...

--Vince

katoranger · 02-15-2009, 10:30 AM

We now have a new forum for off-topic bikes so I will move this there.

I leaning toward the really tight engine.

TeamCheap · 02-15-2009, 11:26 AM

I'm wondering who put it together and if they set the rings with the right clearance or maybe didnt lube it up right on reassembley.

truthfriend7 · 02-15-2009, 04:39 PM

Oh thanks, I didn't realize there was a new forum for non-china bikes. Cool.

Actually I did the rebuild. But I do admit this was my first one. I had a machine shop bore the cylinder 1mm over. I gave them the new piston so they could match it perfectly. I did it by the book and also had some help from an experienced guy too. The end gaps and position of the rings were perfectly in spec. I did wipe oil in the bored cylinder too. However, I didn't know that a new top end would cause hot running and poor fuel mileage though. 20 mpg's seems pretty bad to me. Do you think that's a little too low for a 600?

VinceDrake · 02-15-2009, 05:24 PM

Well, It's a dog of a different stripe, but when I did the top end of my RD the last time (Number 10 at least) I was down to about 15mpg for the first 250 miles or thereabouts. (Takes a really long time with only a 2 gallon tank to get anywheres...)

New top end, new rings, etc. I wouldn't say 20 mpg is unreasonable for the first couple of tanks...

--Vince

truthfriend7 · 02-15-2009, 09:26 PM

Quote:

Originally Posted by VinceDrake

Well, It's a dog of a different stripe, but when I did the top end of my RD the last time (Number 10 at least) I was down to about 15mpg for the first 250 miles or thereabouts. (Takes a really long time with only a 2 gallon tank to get anywheres...)

New top end, new rings, etc. I wouldn't say 20 mpg is unreasonable for the first couple of tanks...

--Vince

What fuel mileage did you get after the initial 250 break-in period? Did it cool off after that as well? I'm wondering if I need to adjust mixture at mid throttle to keep the plug from getting so white in the meantime. But I'd rather not if it's going to work it self out and start running cooler. I like the 2 cycle oil idea. I'll have to try that next tank. Maybe a 60 or 70 to 1 ratio? Thanks.

VinceDrake · 02-15-2009, 10:18 PM

The RD (a 2-stroke Yamaha) Slowly improved from there, about 3mpg more per tank, each tank following. Just the first few sucked completely, and yes it did cool down more and more with the passing of the miles. Each of my china-machines exhibited the same symptoms when new

Since we're on the subject of break in, there's 2 schools of thought, slowly and gently, and ride it like it's going to be ridden. I usually start with the first, and end up doing the second when my throttle hand gets the best of me.

When I light up a new one, I'd say about a 70:1, just enough so there's something there for the valves... But that's just me, others may differ...

(And lots and lots of oil changes... Gotta get the crap out of there...)

--Vince

truthfriend7 · 02-16-2009, 09:26 AM

Yeah, I read a post recommending the motoman break-in method which is basically the "run it hard" school of thought. I did that for the first few miles but then my tale pipe caught on fire. I wondered why the motor was bogging down and why people seemed to be staring more than normal. Just too much crud built up in there over the years. In hindsight, I thought is was kind of cool to be riding around with a big old flame out the back. But just not practical.

I wonder if the effects of a new top end would be the same on a 4 stroke as a 2 cycle? I don't see why it wouldn't. That would be great if the bike doesn't need anything. The motorcycle veteran I talked to the other day thinks I need to check out the ignition timing.

02-15-2009, 07:05 AM	#1
truthfriend7 Join Date: Dec 2007 Location: Florida Posts: 92	My Bike's Overheating, Why? (sorry for the honda question) Let me apologize for asking a question about a non-china bike. I just feel more comfortable asking you guys (being a former china biker myself) and the bikes is a similar design. It's a honda xl600 single cylinder, air-cooled engine with overhead valves. I recently had it bored out with a new piston and lapped the valves. It runs and drives okay, but the spark plug looks too hot. Also I'm only getting about 20 miles-per-gallon. My understanding is that I should be getting twice that. So it must not be a fuel mixture issue because I'm burning through the gas. There's no fuel leaks I can see. I checked the timing and it's perfect. I did notice that one of the intake valves was too tight on the clearance but that's it. Do you think that's what was causing this or something else? Thanks for your help, and don't feel like you need to waste any time looking for an answer. Just if any of you mechanics have something off the top of your head that helps I appreciate it.
	0

02-15-2009, 09:46 AM	#3
VinceDrake Join Date: Nov 2007 Location: Southern Saskatchewan Posts: 491	If it's really recent, the engine could just be that tight. (i.e. between the rings and the bore) A rebuilt engine creates a pile of heat for the first few hundred miles, until things are mated correctly, and more fluid. Also, all that extra friction does destroy fuel mileage. Personally, on a fresh 4 stroke motor-cycle engine I like to throw some 2 stroke oil in the fuel, and a bottle of EOS (A ZDDP additive) just to try to soothe the hot spots, until things get broken in some... --Vince __________________ "Sometimes it is better to say nothing, and let people think you're an idiot, than to open your mouth and prove it."
	0

02-15-2009, 10:30 AM	#4
katoranger Join Date: May 2007 Location: Altamont, Kansas Posts: 15,103	We now have a new forum for off-topic bikes so I will move this there. I leaning toward the really tight engine. __________________ You meet the nicest people on a Honda Clone.
	0

02-15-2009, 05:24 PM	#7
VinceDrake Join Date: Nov 2007 Location: Southern Saskatchewan Posts: 491	Well, It's a dog of a different stripe, but when I did the top end of my RD the last time (Number 10 at least) I was down to about 15mpg for the first 250 miles or thereabouts. (Takes a really long time with only a 2 gallon tank to get anywheres...) New top end, new rings, etc. I wouldn't say 20 mpg is unreasonable for the first couple of tanks... --Vince __________________ "Sometimes it is better to say nothing, and let people think you're an idiot, than to open your mouth and prove it."
	0

02-15-2009, 10:18 PM	#9
VinceDrake Join Date: Nov 2007 Location: Southern Saskatchewan Posts: 491	The RD (a 2-stroke Yamaha) Slowly improved from there, about 3mpg more per tank, each tank following. Just the first few sucked completely, and yes it did cool down more and more with the passing of the miles. Each of my china-machines exhibited the same symptoms when new Since we're on the subject of break in, there's 2 schools of thought, slowly and gently, and ride it like it's going to be ridden. I usually start with the first, and end up doing the second when my throttle hand gets the best of me. When I light up a new one, I'd say about a 70:1, just enough so there's something there for the valves... But that's just me, others may differ... (And lots and lots of oil changes... Gotta get the crap out of there...) --Vince __________________ "Sometimes it is better to say nothing, and let people think you're an idiot, than to open your mouth and prove it."
	0

02-15-2009, 07:56 AM	#2
TeamCheap Join Date: Jun 2006 Location: directly under the earths sun............NOW Posts: 2,302	Who did the reassembly ?
	0

02-15-2009, 11:26 AM	#5
TeamCheap Join Date: Jun 2006 Location: directly under the earths sun............NOW Posts: 2,302	I'm wondering who put it together and if they set the rings with the right clearance or maybe didnt lube it up right on reassembley.
	0

02-15-2009, 04:39 PM	#6
truthfriend7 Join Date: Dec 2007 Location: Florida Posts: 92	Oh thanks, I didn't realize there was a new forum for non-china bikes. Cool. Actually I did the rebuild. But I do admit this was my first one. I had a machine shop bore the cylinder 1mm over. I gave them the new piston so they could match it perfectly. I did it by the book and also had some help from an experienced guy too. The end gaps and position of the rings were perfectly in spec. I did wipe oil in the bored cylinder too. However, I didn't know that a new top end would cause hot running and poor fuel mileage though. 20 mpg's seems pretty bad to me. Do you think that's a little too low for a 600?
	0

02-16-2009, 09:26 AM	#10
truthfriend7 Join Date: Dec 2007 Location: Florida Posts: 92	Yeah, I read a post recommending the motoman break-in method which is basically the "run it hard" school of thought. I did that for the first few miles but then my tale pipe caught on fire. I wondered why the motor was bogging down and why people seemed to be staring more than normal. Just too much crud built up in there over the years. In hindsight, I thought is was kind of cool to be riding around with a big old flame out the back. But just not practical. I wonder if the effects of a new top end would be the same on a 4 stroke as a 2 cycle? I don't see why it wouldn't. That would be great if the bike doesn't need anything. The motorcycle veteran I talked to the other day thinks I need to check out the ignition timing.
	0