Re: Burton cartridge water pump fitment issues
Posted: Sat Mar 23, 2019 1:53 pm
A bit of an update. I can confirm that a QED crankshaft pulley is machined to the correct offset for a Lotus Twin Cam. It's shape (unlike the Burton one) appears almost identical to the original pulley except in steel rather than cast iron. It's quite heavy however. It's heavier than the original cast iron pulley and substantially heavier than the Burton pulley. It doesn't come with the timing mark machined into it either - the Burton one does.
I have now pressed the water pump pulley further onto the shaft so that the water pump and crankshaft pulleys correctly align. I've used the original pulley with it's correct offset rather than the Burton pulley with it's incorrect offset for alignment reference. There's stuff all clearance between the back of the water pump pulley and the water pump cartridge mounting bolts. Certainly the socket head cap screws supplied in the Burton fitting kit are unusable. I expect Burton's have used their pulley with incorrect offset for reference in the design of the front covers for the cartridge water pump parts which hasn't helped the situation either. Doing a few measurements I believe at least another 1.0mm or so could be gained by simply further machining the face of the front cover where the water pump sits.
To try and get around the issue (which let's face it one should not have to do) I've investigated some low profile fastener options. Unfortunately the off the shelf options for low profile heads in combination with imperial threads are much less than with metric threads. I've decided the best option so far it to use some Harley Davidson button head Torx bolts!!. I took a trip down to my closest Harley Davidson dealer (Interesting experience that - never been inside a Harley Davidson dealership before. I felt quite out of place because I didn't have any tattoos!) See picture of the various bolts attached. From left to right we have:
1, Burton supplied 1/4"-20 x 2-1/4" cap screw (2 required for pump mounting. Not possible to use)
2. Harley Davidson P/N 946 Grade 8 1/4"-20 x 2-1/4" Torx head button screws
3. As above except with long shank (Yes same part number - Harley quality is still not yet at Japanese standards!!)
4. Harley Davidson P/N 4232 Grade 8 5/16"-18 x 2-3/4" Torx head button screw
5. Buell (owned by Harley) P/N CA0020.02AB 5/16"-18 x 2-3/8" Torx head button screw
6. Burton supplied 5/16"-18 x 2-1/4" cap screw (1 required for pump mounting. Not possible to use)
Of these I settled on using 3) and also 4) - shortened to 2-1/4". Using these parts the bolt with the least clearance to the back of the pulley is the 5/16" threaded one. It's possible to use either a flat washer or a spring washer under the head but not both. Note Burton supply their front cover with both spring and flat washers for all the fasteners securing their cover. With either a spring or flat washer under the head the clearance to the back of the pulley is about 1.0mm. To my mind at least this is still marginal. Should the water pump bearing wear it's quite likely the pulley will still make contact with this bolt. It seems to be the best solution given the sub-optimal circumstances however.
One last thing. Seniorchristo if you have a Burton front cover I would appreciate if you could measure and advise the distance from the water pump mounting face to the rear face that contacts the backplate. If this is inconsistent from front cover to front cover it also highlights an issue.
I have now pressed the water pump pulley further onto the shaft so that the water pump and crankshaft pulleys correctly align. I've used the original pulley with it's correct offset rather than the Burton pulley with it's incorrect offset for alignment reference. There's stuff all clearance between the back of the water pump pulley and the water pump cartridge mounting bolts. Certainly the socket head cap screws supplied in the Burton fitting kit are unusable. I expect Burton's have used their pulley with incorrect offset for reference in the design of the front covers for the cartridge water pump parts which hasn't helped the situation either. Doing a few measurements I believe at least another 1.0mm or so could be gained by simply further machining the face of the front cover where the water pump sits.
To try and get around the issue (which let's face it one should not have to do) I've investigated some low profile fastener options. Unfortunately the off the shelf options for low profile heads in combination with imperial threads are much less than with metric threads. I've decided the best option so far it to use some Harley Davidson button head Torx bolts!!. I took a trip down to my closest Harley Davidson dealer (Interesting experience that - never been inside a Harley Davidson dealership before. I felt quite out of place because I didn't have any tattoos!) See picture of the various bolts attached. From left to right we have:
1, Burton supplied 1/4"-20 x 2-1/4" cap screw (2 required for pump mounting. Not possible to use)
2. Harley Davidson P/N 946 Grade 8 1/4"-20 x 2-1/4" Torx head button screws
3. As above except with long shank (Yes same part number - Harley quality is still not yet at Japanese standards!!)
4. Harley Davidson P/N 4232 Grade 8 5/16"-18 x 2-3/4" Torx head button screw
5. Buell (owned by Harley) P/N CA0020.02AB 5/16"-18 x 2-3/8" Torx head button screw
6. Burton supplied 5/16"-18 x 2-1/4" cap screw (1 required for pump mounting. Not possible to use)
Of these I settled on using 3) and also 4) - shortened to 2-1/4". Using these parts the bolt with the least clearance to the back of the pulley is the 5/16" threaded one. It's possible to use either a flat washer or a spring washer under the head but not both. Note Burton supply their front cover with both spring and flat washers for all the fasteners securing their cover. With either a spring or flat washer under the head the clearance to the back of the pulley is about 1.0mm. To my mind at least this is still marginal. Should the water pump bearing wear it's quite likely the pulley will still make contact with this bolt. It seems to be the best solution given the sub-optimal circumstances however.
One last thing. Seniorchristo if you have a Burton front cover I would appreciate if you could measure and advise the distance from the water pump mounting face to the rear face that contacts the backplate. If this is inconsistent from front cover to front cover it also highlights an issue.