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37 Posts
Hey everybody -
The VTR250 forum isn't coming up with many answers, so I'm turning to my friends here for help. I think there's a lot more technical knowledge floating around here than over there, so I'm hoping for a fix.
I've had a 1990 VTR250 for about 48 hours now. When I got the bike I got an email from the 2nd owner (I'm 4th) about it.
Bike has 2710 miles and is in perfect condition (other than this problem).
2nd owner had stuck rings, so he had new rings put in, and new front and rear head gaskets.
1st owner rode it for one season then quit.
2nd owner inherited a non-runner, had the carbs rebuilt and tuned, but as it cranks, it'll fire only if the throttle is held wide open. And then it might run for 5 seconds before dying. That's the same thing I'm running into now.
Spark plugs are gapped and have strong spark in both cylinders, so the coils and CDI are fine. Ignition timing could be suspect though.
I did a quick once-over of the carbs after I pulled them last night, but they were *****-n-span clean, no corrosion or chunks of anything. Fuel tank is also perfectly clean on the inside, no rust at all.
Both CV slides are in good shape, move freely, and there are no holes in the diaphragms. The CV slides in this bike have rubber diaphragms and plastic slides, and metal needles, but the plastic slides seem a little stiff when moving up and down.
The PO said he suspected a timing issue (since the 2nd owner pulled the heads). I pulled the valve covers and checked the timing with the rear cylinder at TDC T1 mark, and all the cam sprockets line up with the head surfaces (this is a DOHC engine with chain driven sprockets. 4 cams total, 4 sprockets). I turned it over by hand and the IN/EX valves were opening and closing at the correct times (unless I counted off, but I'm pretty sure I was right).
Today I threw the air filter back on and fired up the bike. It ran at only WOT for 3 or 4 seconds at a time. If you back off the throttle 1/8, it stalls. Rear header pipe was stone cold and the front got warm.
Pulled the air filter and sprayed a bit of starting fluid down each carb throat. Opened each bowl drain to make sure gas was getting to both carbs, but the rear seemed to only have about a teaspoon of gas in it. Seemed suspect to me. Re-pulled the carbs, blew them out with aerosol carb cleaner and compressed air (again), removed all the jets, cleaned them, cleaned the pilot screw holes and adjusted to 2-3/8 turns out (where they were originally). Now I walk inside, eat lunch, have a beer, and walk back out. Now I hit the starter, vrooms to life, revs up to 10k, then starts bogging down almost immediately. For those 5 seconds, it sounded like it should sound. Now, I've been working on Honda motorcycles and riding for 6 years straight.
It seems to be happiest with the choke about half on. Doesn't want to fire with the choke either on or off completely.
Petcock flows well, and now both float bowls fill with the correct amount of gas. Float levels are within exactly 6.8 mm, which is spec. I've had fouled plugs on both cylinders, then replaced, then fouled just the rear, then replaced, then fouled just the front. The front was flooded, then the rear was flooded, and at first, both were flooded.
I don't have any vacuum leaks anywhere either. The needles are in clean and in good shape. Both carbs are 100% perfectly clean. Not a speck of dust anywhere on them, so I have to assume it's something else at this point.
Both headers are still getting hot, but it's still only firing for 4-5 seconds at a time only with the throttle wide open. The rear header got burning hot, which makes me think starting fluid ignited inside the header, which makes me think timing. The front header never got more than hot-to-the-touch. Brand new fresh gas and oil too. If the throttle is held wide open, it's only running at 1500-2k RPM's...not like it's revving.
This thread sounds exactly like what is going on with mine. But checking and rechecking the cam sprockets makes it seem like the marks line up with the top of the head walls evenly.
A rubber sealed compression tester showed 100/120 rear/front, but I could hear blow-by past the rubber seal. My brother will bring over his screw-in compression tester tonight and I should know more then. 188 +/- 28 is the spec, so 160 - 200 is where it should be.
Any suggestions on where to go next? I realize y'all won't be familiar with this engine, but hopefully someone has come across something similar at some point. I did a quick search of the forum but didn't find much.
In a nutshell:
My suspicions are compression, cam timing, or ignition timing. I believe the flooding and fouling plugs are both from WOT starts and idles - too much fuel. Air filter off makes no difference. Bike only starts at WOT, but has fresh gas, clean carbs, low miles, etc.
Bring on some suggestions!! I'll try just about anything at this point.
Thanks in advance!
--jinbtown
The VTR250 forum isn't coming up with many answers, so I'm turning to my friends here for help. I think there's a lot more technical knowledge floating around here than over there, so I'm hoping for a fix.
I've had a 1990 VTR250 for about 48 hours now. When I got the bike I got an email from the 2nd owner (I'm 4th) about it.
Bike has 2710 miles and is in perfect condition (other than this problem).
2nd owner had stuck rings, so he had new rings put in, and new front and rear head gaskets.
1st owner rode it for one season then quit.
2nd owner inherited a non-runner, had the carbs rebuilt and tuned, but as it cranks, it'll fire only if the throttle is held wide open. And then it might run for 5 seconds before dying. That's the same thing I'm running into now.
Spark plugs are gapped and have strong spark in both cylinders, so the coils and CDI are fine. Ignition timing could be suspect though.
I did a quick once-over of the carbs after I pulled them last night, but they were *****-n-span clean, no corrosion or chunks of anything. Fuel tank is also perfectly clean on the inside, no rust at all.
Both CV slides are in good shape, move freely, and there are no holes in the diaphragms. The CV slides in this bike have rubber diaphragms and plastic slides, and metal needles, but the plastic slides seem a little stiff when moving up and down.
The PO said he suspected a timing issue (since the 2nd owner pulled the heads). I pulled the valve covers and checked the timing with the rear cylinder at TDC T1 mark, and all the cam sprockets line up with the head surfaces (this is a DOHC engine with chain driven sprockets. 4 cams total, 4 sprockets). I turned it over by hand and the IN/EX valves were opening and closing at the correct times (unless I counted off, but I'm pretty sure I was right).
Today I threw the air filter back on and fired up the bike. It ran at only WOT for 3 or 4 seconds at a time. If you back off the throttle 1/8, it stalls. Rear header pipe was stone cold and the front got warm.
Pulled the air filter and sprayed a bit of starting fluid down each carb throat. Opened each bowl drain to make sure gas was getting to both carbs, but the rear seemed to only have about a teaspoon of gas in it. Seemed suspect to me. Re-pulled the carbs, blew them out with aerosol carb cleaner and compressed air (again), removed all the jets, cleaned them, cleaned the pilot screw holes and adjusted to 2-3/8 turns out (where they were originally). Now I walk inside, eat lunch, have a beer, and walk back out. Now I hit the starter, vrooms to life, revs up to 10k, then starts bogging down almost immediately. For those 5 seconds, it sounded like it should sound. Now, I've been working on Honda motorcycles and riding for 6 years straight.
It seems to be happiest with the choke about half on. Doesn't want to fire with the choke either on or off completely.
Petcock flows well, and now both float bowls fill with the correct amount of gas. Float levels are within exactly 6.8 mm, which is spec. I've had fouled plugs on both cylinders, then replaced, then fouled just the rear, then replaced, then fouled just the front. The front was flooded, then the rear was flooded, and at first, both were flooded.
I don't have any vacuum leaks anywhere either. The needles are in clean and in good shape. Both carbs are 100% perfectly clean. Not a speck of dust anywhere on them, so I have to assume it's something else at this point.
Both headers are still getting hot, but it's still only firing for 4-5 seconds at a time only with the throttle wide open. The rear header got burning hot, which makes me think starting fluid ignited inside the header, which makes me think timing. The front header never got more than hot-to-the-touch. Brand new fresh gas and oil too. If the throttle is held wide open, it's only running at 1500-2k RPM's...not like it's revving.
This thread sounds exactly like what is going on with mine. But checking and rechecking the cam sprockets makes it seem like the marks line up with the top of the head walls evenly.
A rubber sealed compression tester showed 100/120 rear/front, but I could hear blow-by past the rubber seal. My brother will bring over his screw-in compression tester tonight and I should know more then. 188 +/- 28 is the spec, so 160 - 200 is where it should be.
Any suggestions on where to go next? I realize y'all won't be familiar with this engine, but hopefully someone has come across something similar at some point. I did a quick search of the forum but didn't find much.
In a nutshell:
My suspicions are compression, cam timing, or ignition timing. I believe the flooding and fouling plugs are both from WOT starts and idles - too much fuel. Air filter off makes no difference. Bike only starts at WOT, but has fresh gas, clean carbs, low miles, etc.
Bring on some suggestions!! I'll try just about anything at this point.
Thanks in advance!
--jinbtown
