Topic: Jets R us carb kits?

[matt167]

I have a set of 4-1 brand carb kits, but I know the brass is junk in them.  I thought I would be able to use my original brass, but only the pilot jets might be savable. The needles and seats are garbage..  It looks like Jets R us sells kits with OEM brass, at around double the cost.. But are they worth it?

[PeWe]

Even the 4-1 pilot jets are junk. Compare with Keihin stock.
2 of 4 pilot jets for my CB750 carbs broke inside. I had to drill the debris out.

Only reason using them was a test with bigger, 42.5.
The carbs have all old stock jets. They work fine after 100.000 km.

[matt167]

Even the 4-1 pilot jets are junk. Compare with Keihin stock.
2 of 4 pilot jets for my CB750 carbs broke inside. I had to drill the debris out.

Only reason using them was a test with bigger, 42.5.
The carbs have all old stock jets. They work fine after 100.000 km.

Do you know if it's true that Jets R us kits are in fact OEM? 

I can probably save my pilot jets, but I had to destroy the needle and seat, and main jets ( and floats actually ) to get them out..  These carbs were left full for 35 years, and what was left was pure glue

[ekpent]

Even the 4-1 pilot jets are junk. Compare with Keihin stock.
2 of 4 pilot jets for my CB750 carbs broke inside. I had to drill the debris out.

Only reason using them was a test with bigger, 42.5.
The carbs have all old stock jets. They work fine after 100.000 km.

Do you know if it's true that Jets R us kits are in fact OEM? 

I can probably save my pilot jets, but I had to destroy the needle and seat, and main jets ( and floats actually ) to get them out..  These carbs were left full for 35 years, and what was left was pure glue

Heat gun along with real carb cleaner from the large dunk cans would have been your friend there to save the old parts. Maybe try on the next project 

[matt167]

Even the 4-1 pilot jets are junk. Compare with Keihin stock.
2 of 4 pilot jets for my CB750 carbs broke inside. I had to drill the debris out.

Only reason using them was a test with bigger, 42.5.
The carbs have all old stock jets. They work fine after 100.000 km.

Do you know if it's true that Jets R us kits are in fact OEM? 

I can probably save my pilot jets, but I had to destroy the needle and seat, and main jets ( and floats actually ) to get them out..  These carbs were left full for 35 years, and what was left was pure glue

Heat gun along with real carb cleaner from the large dunk cans would have been your friend there to save the old parts. Maybe try on the next project 

I have a dunk tank and tried it. There was just no way to get the old parts out of the carbs.. I had to boil the carbs in lemon juice/ water mix to get the slides free.  I'm reasonably sure the Jets R us kits are OEM or quality.. I can still find the parts OEM although the needle and seat are spendy

[jaytee-nz]

I believe the Jets R Us parts were genuine Keihin, but I recall a recent post by someone who had bought a set and then thought they weren't genuine.
I've used Yamiya's kits and they are excellent quality.

[matt167]

I believe the Jets R Us parts were genuine Keihin, but I recall a recent post by someone who had bought a set and then thought they weren't genuine.
I've used Yamiya's kits and they are excellent quality.

I guess, so the question becomes, is the 4-1 needle valve a workable piece?  OEM jets can be had off Amazon, or likely the local dealer if I want to wait, for about $10 each..  But Needle valves, are about $40 each for OEM..  I get jets, generally being re usable but needles are a wear item anyway

[PeWe]

I cleaned mine with naphta followed by a vinegar bath for a few hours.
Drive chain cleaner spray another good cleaning chemical for carbs and jets. (Dirty oil pumps too)
Motorex the best so far.
https://www.motorexusa.com/products/chain-clean-degreaser

I have also tested Motul and A9.

[matt167]

Boiling in a very light lemon juice solution works wonders. It won't pull thick gunk out of the float bowls, but the berrymans does.. But Berrymans would not un stick the slides

What does everyone do for jet up sizing?   I think I'm going to put universal slip on's the original 4-4 just to get it going down the road with the original air filter so jetting will stay stock, but if Jets R us is no longer OEM, and the Honda part numbers for 105 and 110's are NLA  ( factory 40's and 100's are available ). What does someone do?

[jonda500]

I have 105 main jets in both my 500's - found them on ebay -not cheap, but I needed them and they're genuine keihin. Why both my all original bikes need oversize mains I don't know! - like why jetsrus wont ship international, also idk...
John

[gmoss]

I believe the Jets R Us parts were genuine Keihin, but I recall a recent post by someone who had bought a set and then thought they weren't genuine.
I've used Yamiya's kits and they are excellent quality.

I guess, so the question becomes, is the 4-1 needle valve a workable piece?  OEM jets can be had off Amazon, or likely the local dealer if I want to wait, for about $10 each..  But Needle valves, are about $40 each for OEM..  I get jets, generally being re usable but needles are a wear item anyway

I recently purchased a 4-1 carb rebuild kit for a CB500.

Float needles/valves are a different size than stock -- a mm or two larger. Air mixture screws are a different size from stock. Main and pilot jets are the same size as stock, but the pilot jets break very easily.

I cannot vouch for whether the replacement needle valves will work if you figure out a new adjusted travel height for the float, because after a lot of frustration I went back and cleaned the stock float valves to re-use (and then also had to find a source for Keihin slow jets).

[matt167]

I have 105 main jets in both my 500's - found them on ebay -not cheap, but I needed them and they're genuine keihin. Why both my all original bikes need oversize mains I don't know! - like why jetsrus wont ship international, also idk...
John

Interesting.. I found the Jet series number 99202-601 and managed to find Niche cycle supply has OEM listings all the way to #150.  I ordered 4 #105's and I will see if they are genuine or not. JetsRus confirms that they are selling reproductions, as Keihn has discontinued making them


I've got the carbs rebuilt except for floats which I am waiting on. I had to destructively remove the originals to save the towers from possible damage but they might not have floated anyway.. I put the main and secondary jets out of the kit for now. The secondary seems to be identical to the originals. Mains could have actually been re used but the new ones fit fine and I see no difference..  I had to use one emulsion tube as well, as I broke the cleaning rod off that I was using to clean the holes out in the tube

[matt167]

I believe the Jets R Us parts were genuine Keihin, but I recall a recent post by someone who had bought a set and then thought they weren't genuine.
I've used Yamiya's kits and they are excellent quality.

I guess, so the question becomes, is the 4-1 needle valve a workable piece?  OEM jets can be had off Amazon, or likely the local dealer if I want to wait, for about $10 each..  But Needle valves, are about $40 each for OEM..  I get jets, generally being re usable but needles are a wear item anyway

I recently purchased a 4-1 carb rebuild kit for a CB500.

Float needles/valves are a different size than stock -- a mm or two larger. Air mixture screws are a different size from stock. Main and pilot jets are the same size as stock, but the pilot jets break very easily.

I cannot vouch for whether the replacement needle valves will work if you figure out a new adjusted travel height for the float, because after a lot of frustration I went back and cleaned the stock float valves to re-use (and then also had to find a source for Keihin slow jets).

What problems did you have with the needle valve?  Genuine Keihn is available although NOS at this point for about $30/ set. You can use the Honda part number to find it...  My Originals were beyond use, so I have the 4-1 needle valve in place. I understand the float tang will need adjusted for the correct float height

[PeWe]

I have ordered jets from Niche cycle supply, correct Mikuni TMR pilot jets.  A square before size.

I have also ordered Keihin stock jets in a few sizes from eBay UK. OK price.

Aftermarket pilot (TMR) and main jets to Mikuni work well. Pilots are branded EBC. Main no name.

The aftermarket jets to the old keihin carbs seems to be crap or just different despite sold as a repairkit.

The cheap CB750 kits from Cruzinimage look better when looking at the pilot jet. Round holes, not as the 4-1 jets that had holes looked to be stamped, more triangular then round. The needles look leaner at low lifts though.

Same with the latest ultra cheap kits I ordered from Taiwan for rubber gaskets only. Pilot jets do not look that bad as the ones I got from 4-1  I ordered to get a bigger size.

https://www.ebay.com/itm/4X-70-76-cb750-cb-750-k1-k6-Carb-Carburetor-Rebuild-Repair-Kit-for-48-1908-/222643363184?_trksid=p2349624.m46890.l49286

[matt167]

I compared the 4-1 pilots and they don't look terrible. I stuck them in for now, but the bowls are off so it's not a big deal to change them if I find NOS.

[gmoss]

What problems did you have with the needle valve?  Genuine Keihn is available although NOS at this point for about $30/ set. You can use the Honda part number to find it...  My Originals were beyond use, so I have the 4-1 needle valve in place. I understand the float tang will need adjusted for the correct float height

Because the 4-1 needle valve and sleeve are taller than the original (at least in the set that I got, who knows what their QA and consistency are like), setting the float to the factory heigh will actually result in a lower level of gas closing the needle valve. You'd need to take some very accurate measurements and trig calculations to figure out the new, correct float height.

[matt167]

What problems did you have with the needle valve?  Genuine Keihn is available although NOS at this point for about $30/ set. You can use the Honda part number to find it...  My Originals were beyond use, so I have the 4-1 needle valve in place. I understand the float tang will need adjusted for the correct float height

Because the 4-1 needle valve and sleeve are taller than the original (at least in the set that I got, who knows what their QA and consistency are like), setting the float to the factory heigh will actually result in a lower level of gas closing the needle valve. You'd need to take some very accurate measurements and trig calculations to figure out the new, correct float height.

Makes sense. I'll probably have to bend the tang to get it close, just to get the engine running

[Speedfreak70]

I recently purchased some carb rebuild kits from four into one and let me tell you that stuff is junk
 The needles and seats never would seal which is the main reason I bought this kit
 They sent me four main Jets three marked 100 one marked 78
 They wanted to know if I would prefer to get a replacement or my money back LMAO guess which I went for

[Shtonecb500]

I used carb kits from scrambler cycle
https://scramblercycle.com/collections/honda-cb750-sohc/products/4x-honda-71-76-cb750k-cb750-k1-k6-carburetor-carb-rebuild-kit-4-kits

[matt167]

The #105 jets from Niche cycle appear to be genuine. Slightly tarnished like they have been sitting in a bin for a while and of a much better quality than the copies. If they are copies, they are older, better copies.  I cannot see the Keihn symbol on them

[matt167]

I can confirm that, the jets from Niche cycle appear to be genuine when directly compared to a 4-1 jet, they are very different.  I could not find pilot jets on Niche cycle. I've got my original #40's soaking one last time to try and clean them up but I've got floats now and my carbs are ready to go otherwise

[WhyNot2]

I'm working mine too........

[PeWe]

That amount of white powder when carbs where parked  with 10% ethanol fuel?

My old carbs had a red slimy goo inside after +20 years with non ethanol fuel as it got 1990.

[matt167]

Mine was red stuff as well. I agree that is ethanol residue..

I tried hard to save the original #40 pilots, but I couldn't get 2 of them clear.  I could run a wire through them, but ultimately that would open the hole and cause a tuning issue

[ekpent]

I'm working mine too........

Looks more like a water problem.