fastbroshi Posted November 11, 2023 Share Posted November 11, 2023 It appears this type of petcock was only used in the 3rd/4th gens, and it is no longer available from Honda. Conveniently this style looks to be somewhat unique and doesn't look as if other types are readily adaptable. I have some ideas, but I'd like to know what anyone else has tried. Quote Link to comment Share on other sites More sharing options...
Member Contributer Dutchy Posted November 11, 2023 Member Contributer Share Posted November 11, 2023 On the 4th gen (never owned a 3rd gen) this switch is located under the tank, so unlike the VF500F's (which is on the LHS of the tank and has ON//OFF/RES), you only switch the 4th Gen's to OFF if you want to remove the tank. NRP in the UK sells https://nrp-carbs.co.uk/shop/index.php?route=product/search&search=vfr750 The inlinle "strainer" you could replace with an external filter, or leave it out altogether. Quote Link to comment Share on other sites More sharing options...
Member Contributer jefferson Posted November 11, 2023 Member Contributer Share Posted November 11, 2023 Attack of the ethanol demons. Quote Link to comment Share on other sites More sharing options...
Member Contributer bmart Posted November 12, 2023 Member Contributer Share Posted November 12, 2023 Our government insists that ethanol is fine. You probably just have a broken camera...or broken eyes. Quote Link to comment Share on other sites More sharing options...
Member Contributer jefferson Posted November 12, 2023 Member Contributer Share Posted November 12, 2023 I'm not much of a believer in what kind of tripe the government spews. Quote Link to comment Share on other sites More sharing options...
Member Contributer JZH Posted November 13, 2023 Member Contributer Share Posted November 13, 2023 The petcock is interesting. I'm not 100% sure about the 4th gens, but Honda used the same petcock on all 3rd gens, whether they had the US-style "no reserve" or the ROW's remote reserve switch (but no low fuel light). (The "MT4" on the strainer tube suggests that the part is the same across all 3rd and 4th gens, however.) The difference at the petcock was in the knob used: the US-spec knob goes from OFF to ON, with RES being blocked. The difference between ON and RES is simply which inlet is directed to the petcock's output. But that only works when the OEM fuel strainer tubes are fitted, which make the ON inlet effectively a couple of inches higher than the RES inlet within the fuel tank. So, on non-US-Spec bikes, when the switch is ON and the fuel level drops to the level of the ON inlet on the strainer tube, the engine sputters--prompting the rider to turn the switch to RES (ideally in one swift move without breaking stride)--which then allows the RES inlet at the bottom of the tank feed the remaining fuel in the tank to the carbs. US-spec bikes only use one of the inlets (the RES, which is the lower one), which means that if your OEM fuel strainer tube falls to bits all you really need to do is fit a strainer/mesh to the RES inlet on the petcock and you'll have "full US-spec" functionality again. Or don't fit anything and rely on your fuel filter? (Not what I would suggest!) However, the petcock itself might be past its prime, but it can be rebuilt using common o-rings. Drill out the two rivets and tap the holes for M4 (I think it was--whatever is smallest that allows threads to be tapped). NRP in the UK sells dedicated rebuild kits, but any o-rings (which fit) can be used in a pinch. Unlike earlier petcocks which use special-sized seals, this model only uses round ones. With some trial and error, and a good selection of fuel-resistant o-rings in different sizes, you can rebuild these petcocks to again function perfectly. Ciao, JZH 1 Quote Link to comment Share on other sites More sharing options...
fastbroshi Posted November 13, 2023 Author Share Posted November 13, 2023 On 11/11/2023 at 1:18 AM, Dutchy said: On the 4th gen (never owned a 3rd gen) this switch is located under the tank, so unlike the VF500F's (which is on the LHS of the tank and has ON//OFF/RES), you only switch the 4th Gen's to OFF if you want to remove the tank. NRP in the UK sells https://nrp-carbs.co.uk/shop/index.php?route=product/search&search=vfr750 The inlinle "strainer" you could replace with an external filter, or leave it out altogether. Dutchy, I will look at that petcock and verify if it interchanges. If so Honda needs to update their parts diagram supercede #! My current plan, if the VF500 version isn't viable, is to break off the remaining filter plastic, leaving just the base. This appears that it will still seal when seated properly with a new o-ring. I'm going to take some stainless pipes and cut them to length to mimic the height of the plastic filter's cylinders. Cut windows in them and cover with stainless mesh, epoxy in place. Mate the pipes to the plastic base with epoxy, being careful to not mount too deep and keeping total height in mind. Cap the pipes with stainless plugs. If I had a lathe I wouldn't have to use the original plastic base and just turn it out of stainless, drill two holes for the tubes, etc. But I have no practical lathe experience either lol. On 11/11/2023 at 9:12 AM, jefferson said: Attack of the ethanol demons. Precisely. The bike hasn't had a full tank ran through it in over 5 years. 7 hours ago, JZH said: The petcock is interesting. I'm not 100% sure about the 4th gens, but Honda used the same petcock on all 3rd gens, whether they had the US-style "no reserve" or the ROW's remote reserve switch (but no low fuel light). (The "MT4" on the strainer tube suggests that the part is the same across all 3rd and 4th gens, however.) The difference at the petcock was in the knob used: the US-spec knob goes from OFF to ON, with RES being blocked. The difference between ON and RES is simply which inlet is directed to the petcock's output. But that only works when the OEM fuel strainer tubes are fitted, which make the ON inlet effectively a couple of inches higher than the RES inlet within the fuel tank. So, on non-US-Spec bikes, when the switch is ON and the fuel level drops to the level of the ON inlet on the strainer tube, the engine sputters--prompting the rider to turn the switch to RES (ideally in one swift move without breaking stride)--which then allows the RES inlet at the bottom of the tank feed the remaining fuel in the tank to the carbs. US-spec bikes only use one of the inlets (the RES, which is the lower one), which means that if your OEM fuel strainer tube falls to bits all you really need to do is fit a strainer/mesh to the RES inlet on the petcock and you'll have "full US-spec" functionality again. Or don't fit anything and rely on your fuel filter? (Not what I would suggest!) However, the petcock itself might be past its prime, but it can be rebuilt using common o-rings. Drill out the two rivets and tap the holes for M4 (I think it was--whatever is smallest that allows threads to be tapped). NRP in the UK sells dedicated rebuild kits, but any o-rings (which fit) can be used in a pinch. Unlike earlier petcocks which use special-sized seals, this model only uses round ones. With some trial and error, and a good selection of fuel-resistant o-rings in different sizes, you can rebuild these petcocks to again function perfectly. Ciao, JZH Thankfully the o-rings appear to only seal the on/off knob's shaft. Those are not leaking. After I cleaned out all of the sulfur looking powder, I was able to verify it still seals properly when turned off and flows when on. Quote Link to comment Share on other sites More sharing options...
fastbroshi Posted November 13, 2023 Author Share Posted November 13, 2023 After some more looking, it appears the '97-'98 Blackbird petcocks have an identical base to the VFR's. The outside is much different, but compare the base in this link to the base of my petcock above: https://www.partzilla.com/product/honda/16950-MBB-642?gad=1&gclid=Cj0KCQiAr8eqBhD3ARIsAIe-buMLcc0849cy69Jp2TGBxd2vogww_dy_pZGjRKI8oVmf-6V9_jvsQKoaAlwaEALw_wcB I'm convinced the filter for this petcock would work, but I can't find a separate one just yet and I don't want to spend over $200 to test my theory. Does anyone have a spare carb'ed Blackbird petcock just lying around? Quote Link to comment Share on other sites More sharing options...
Member Contributer Captain 80s Posted November 13, 2023 Member Contributer Share Posted November 13, 2023 Same part number used on the VTR1000F. Perhaps that will increase your search area. There is a used one on eBay, maybe they will take a measurement for you. eBay VTR petcock Quote Link to comment Share on other sites More sharing options...
fastbroshi Posted November 13, 2023 Author Share Posted November 13, 2023 So it looks like I misread the parts listing and if part # 16952-MBB-003 (both the Blackbird and Superhawk filter; you're correct Captain) was available. The filter looks like it will fit. I just ordered a vendor on ebay's last one. Fingers crossed it fits ok. Quote Link to comment Share on other sites More sharing options...
Member Contributer Captain 80s Posted November 13, 2023 Member Contributer Share Posted November 13, 2023 Please update with some dimensions when you receive. Quote Link to comment Share on other sites More sharing options...
Member Contributer JZH Posted November 17, 2023 Member Contributer Share Posted November 17, 2023 On 11/13/2023 at 5:55 PM, fastbroshi said: My current plan, if the VF500 version isn't viable, is to break off the remaining filter plastic, leaving just the base. This appears that it will still seal when seated properly with a new o-ring. I'm going to take some stainless pipes and cut them to length to mimic the height of the plastic filter's cylinders. Cut windows in them and cover with stainless mesh, epoxy in place. Mate the pipes to the plastic base with epoxy, being careful to not mount too deep and keeping total height in mind. Cap the pipes with stainless plugs. You wouldn't need to make any tubes--just a filter/strainer. Your US-spec setup only uses the RES and OFF positions on the petcock, so why wouldn't you want the pick-up point to be as low as possible in the tank? I have rebuilt these petcocks before. Good luck. Ciao, JZH Quote Link to comment Share on other sites More sharing options...
Andy72210 Posted December 27, 2023 Share Posted December 27, 2023 On 11/13/2023 at 12:22 PM, Captain 80s said: Same part number used on the VTR1000F. Perhaps that will increase your search area. There is a used one on eBay, maybe they will take a measurement for you. eBay VTR petcock Cap'n, My VTR uses vacuum to begin the flow...not sure if the VFR does this also? And, the VTR is susceptible to vacuum issues as well. Quote Link to comment Share on other sites More sharing options...
Member Contributer Captain 80s Posted December 27, 2023 Member Contributer Share Posted December 27, 2023 1 hour ago, Andy72210 said: Cap'n, My VTR uses vacuum to begin the flow...not sure if the VFR does this also? And, the VTR is susceptible to vacuum issues as well. I think you may have skipped a step when reading this thread. - OP has bad VFR petcock - OP comments on how XX is the same base as VFR - My comment that the VTR is same part # as XX to widen search (that's it) Also. the vacuum operation is easily deleted. I do it on my 500 Interceptors. Quote Link to comment Share on other sites More sharing options...
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