Vintage J-Model Whizzer
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Mike Notigan
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Ditto!
Mike
Mike
Paula
Member
Thanks for those pictures, Ray -- you've got some beautiful Whizzers there!
Hope everyone had a nice Thanksgiving holiday!
Paula
Hope everyone had a nice Thanksgiving holiday!
Paula
Paula
Member
Carburetor
Hi again,
Finally got a break from work in the last few weeks. Things are getting somewhat back to normal, so I had some time to spend on the Whizzer. The next item of interest is the carburetor. Here are a few photos of the carburetor that was on the bike when I got it:
Some of you will have noticed that this is not the "correct" carburetor for this engine (or any Whizzer engine, for that matter.) It is a Tillotson MT8A. I believe that the correct carb for this engine, based on the J-204166 serial number, would have been the Carter N655S or N666S ("fixed-jet" versions.) Obviously, the original was replaced at some point. Nevertheless, it seems that many miles were racked up on this engine using the MT8A, so it must have been at least somewhat compatible with the Whizzer "J" engine.
The Tillotson MT8A appears to be a scaled-down version of the MT12A, which is the correct carburetor for the later, larger-valved engines. The MT8A has a 7/16" venturi, which is correct for the "J" engine, and it does feature an adjustable main jet. How well it suits this engine in other technical respects, I'm not competent to say. Note, however, that the fuel inlet is on the side of the carburetor, which differs from the Whizzer-specific carbs, which all have fuel inlets on the top. Presumably, this makes for easier routing of the fuel hose to the tank outlet, which is on the opposite side of the bike.
Another difference: the choke lever is shifted 90 degrees from the normal Whizzer position, such that it seems to be designed to be operated from the left side of the carburetor (when mounted on a Whizzer engine.) Also, note that the main needle is equipped with a graduated knob which faces the left side as well. The throttle shaft has a torsion-spring return, indicating that it may have been designed for use with a governor. On the other hand, the MT8A has a slotted base, and fits the Whizzer "J" engine carburetor flange nicely.
Though I'm not an absolute stickler for originality, I don't like straying too far from the original configuration either. Should I stick with the MT8A for this project, or try to acquire the correct carburetor? From what I've seen, even mediocre examples seem to command high prices, decent ones even more. I don't have a lot of spare cash to invest in this project right now, so I'm going to go ahead and clean up the MT8A, and see if it even warrants consideration. In the meantime, I'll keep my eyes open for a suitable Carter âœN" carburetor.
More to come.
Hi again,
Finally got a break from work in the last few weeks. Things are getting somewhat back to normal, so I had some time to spend on the Whizzer. The next item of interest is the carburetor. Here are a few photos of the carburetor that was on the bike when I got it:
Some of you will have noticed that this is not the "correct" carburetor for this engine (or any Whizzer engine, for that matter.) It is a Tillotson MT8A. I believe that the correct carb for this engine, based on the J-204166 serial number, would have been the Carter N655S or N666S ("fixed-jet" versions.) Obviously, the original was replaced at some point. Nevertheless, it seems that many miles were racked up on this engine using the MT8A, so it must have been at least somewhat compatible with the Whizzer "J" engine.
The Tillotson MT8A appears to be a scaled-down version of the MT12A, which is the correct carburetor for the later, larger-valved engines. The MT8A has a 7/16" venturi, which is correct for the "J" engine, and it does feature an adjustable main jet. How well it suits this engine in other technical respects, I'm not competent to say. Note, however, that the fuel inlet is on the side of the carburetor, which differs from the Whizzer-specific carbs, which all have fuel inlets on the top. Presumably, this makes for easier routing of the fuel hose to the tank outlet, which is on the opposite side of the bike.
Another difference: the choke lever is shifted 90 degrees from the normal Whizzer position, such that it seems to be designed to be operated from the left side of the carburetor (when mounted on a Whizzer engine.) Also, note that the main needle is equipped with a graduated knob which faces the left side as well. The throttle shaft has a torsion-spring return, indicating that it may have been designed for use with a governor. On the other hand, the MT8A has a slotted base, and fits the Whizzer "J" engine carburetor flange nicely.
Though I'm not an absolute stickler for originality, I don't like straying too far from the original configuration either. Should I stick with the MT8A for this project, or try to acquire the correct carburetor? From what I've seen, even mediocre examples seem to command high prices, decent ones even more. I don't have a lot of spare cash to invest in this project right now, so I'm going to go ahead and clean up the MT8A, and see if it even warrants consideration. In the meantime, I'll keep my eyes open for a suitable Carter âœN" carburetor.
More to come.
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Paula
Member
Got the MT8A all disassembled and cleaned up. I was pleasantly surprised at how good everything looked. No signs of abuse or excessive wear. The throttle shaft shows some wear, but only on the order of a few thousandths, which is well within the usable range. The needle valves and seats look fine, as do all of the float valve components. The float has no leaks. Here's a view of the body casting, all cleaned up:
As mentioned earlier, the MT8A has the fuel inlet on the right side of the bowl, rather than the top. I decided to go ahead and rectify this situation. There was a cast hose barb on the side of the bowl, for directly connecting the fuel hose. I sawed the barb off, faced the casting, and drilled & tapped the hole for a small brass plug:
Step 2 involved drilling and tapping a hole directly over the float valve, and making an adapter with a 1/8" NPT thread to accommodate the standard fuel hose elbow. The adapter was lathe turned from a short length of 1/2" hex brass:
The fuel bowl gasket was looking pretty ragged, so I decided that it should be replaced. I had no idea where to obtain one, so I went ahead and made one out of some 1/32" thick gasket sheet (the old gasket is on the right):
In case anyone's wondering, a good way to make such a gasket is to drill appropriately-sized holes at all the necessary points, including the corners of internal openings. To make the holes come out clean, clamp the gasket material between two aluminum plates when drilling. After the holes are done, the rest of the profile can be easily cut with an X-acto knife:
Another thing I did was replace the original fixed throttle lever with the correct, adjustable version (it came from an ML5B parts carb.) All the parts went together well. The packing for the main adjustment needle is still good, and seals well when the packing nut is tightened. The original bowl screws and lockwashers were replaced with stainless versions.
With the MT8A all back together, I did a trial-fitting on the partially-assembled engine. It looks good:
I think this carburetor will work well with the "J" engine, but I still want to look into getting a more correct version. Hopefully, I can find one fairly reasonably that only needs some TLC to make it right. My fingers are crossed.
Paula
As mentioned earlier, the MT8A has the fuel inlet on the right side of the bowl, rather than the top. I decided to go ahead and rectify this situation. There was a cast hose barb on the side of the bowl, for directly connecting the fuel hose. I sawed the barb off, faced the casting, and drilled & tapped the hole for a small brass plug:
Step 2 involved drilling and tapping a hole directly over the float valve, and making an adapter with a 1/8" NPT thread to accommodate the standard fuel hose elbow. The adapter was lathe turned from a short length of 1/2" hex brass:
The fuel bowl gasket was looking pretty ragged, so I decided that it should be replaced. I had no idea where to obtain one, so I went ahead and made one out of some 1/32" thick gasket sheet (the old gasket is on the right):
In case anyone's wondering, a good way to make such a gasket is to drill appropriately-sized holes at all the necessary points, including the corners of internal openings. To make the holes come out clean, clamp the gasket material between two aluminum plates when drilling. After the holes are done, the rest of the profile can be easily cut with an X-acto knife:
Another thing I did was replace the original fixed throttle lever with the correct, adjustable version (it came from an ML5B parts carb.) All the parts went together well. The packing for the main adjustment needle is still good, and seals well when the packing nut is tightened. The original bowl screws and lockwashers were replaced with stainless versions.
With the MT8A all back together, I did a trial-fitting on the partially-assembled engine. It looks good:
I think this carburetor will work well with the "J" engine, but I still want to look into getting a more correct version. Hopefully, I can find one fairly reasonably that only needs some TLC to make it right. My fingers are crossed.
Paula
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Mike Notigan
Member
- Local time
- 9:43 PM
- Joined
- Mar 10, 2011
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- 56
Great to see with the coming of spring a Paula Post! Beautiful work, as usual on the carb rebuild. "Though I’m not an absolute stickler for originality"...... Right!
Lovely work, all the same! Welcome back!
@Ray: Beautiful bikes, too! Makes me itch for the day I break down and get a motorcycle license for the old NER and hit the road with her!
Take Care,
Mike
Lovely work, all the same! Welcome back!@Ray: Beautiful bikes, too! Makes me itch for the day I break down and get a motorcycle license for the old NER and hit the road with her!
Take Care,
Mike
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