Throttle bodies interchangeable?

[DennisA]

My 2001 5th gen problems are being addressed by starting with throttle bodies complete with fuel rails and injectors. There are multiple units available from a 98 or 99. The part number is slightly different. Can anyone tell me if it will fit or what the difference is?

 

Thanks,

Dennis 

[Lorne]

Physically, the '98/'99 TB ought to fit. But, they lack the automatic enricher and require a fast idle lever in the left handlebar switch housing.

 

Possible that you could mix & match but my guess is that a good mechanic ought to be able to diagnose the fault in your current unit.

 

What problem are you trying to solve? Symptoms?

[Cogswell]

+1

 

But if you do get a 98/99 unit, you need to replace the left side horn /  headlight switch unit and run the cable down to the TB.  Personally, I'm no fan of the wax unit on my 6th gen - I much prefer the manual control over the fast idle I have on my '99.  I've even mulled over seeing if I could convert the 6th gen - hasn't happened so far.   YMMV.

 

[KevCarver]

+2

I prefer the lever on my ‘99 over wax unit. 

I’d say it should work, just cap your coolant line to the wax unit, and find a lever and cable. You should be able to add it to your left switch pod, as I think they only use a blocking plate rather than a different pod. 

[DennisA]

This is my 5th VFR (3rd 5th gen) and the throttle response is erratic. It bogs down at 4,000 rpm sometimes but the surging is the biggest problem. Previous bikes were linear in power with predictable boost around 7,500 rpm and fully powered up at 9,000. My new 2001 sat for a couple of years before I purchased it. I've changed plugs, gas, oil and air filters, switched to synthetic oil, flushed the cooling system with little improvement. About 8,000 miles, mostly highway with 4 tanks having Techron additive in the past month. Not sure if o2 sensor eliminator would help before I tackle the throttle bodies and injectors. I checked the stator at 12.75 on the bench then approx. 14.5 with the bike fast idling.

 

Running out of summer...….

[MadScientist]

Two potential mechanical culprits this sounds kind of like:

1. Vacuum leak - those lines are almost 20 years old.  When I rebuilt mine there were a few questionable looking lines.

2.  Fuel Pressure Regulator - the internal vacuum diaphragm and gaskets break down leading to fuel pouring through the vacuum line and into the #3 cylinder throttle body.

 

Could be electrical gremlins or dirty injectors.  Additionally, if the bike sat for some years, there may have been rust in the tank that subsequently plugged up the in-tank fuel filter.

 

I'd lay off the O2 sensors for now.  Eliminating them may identify the O2 sensors as the culprit, but it may also make diagnosis more troublesome. 

[DennisA]

You were correct about the throttle bodies being different. I ended up purchasing on eBay throttle bodies for my 01 ($120) and then a set from a 98 ($100) model because it had the interchangeable fuel rails and injectors included. We cleaned the throttle bodies and serviced the best 4 injectors then re-installed only to discover there was no power to the fuel pump. Out it came again, repair and test the connection mentioned plus the 4 to the injectors then re-install. Pleased to say the bike is running much better, especially when cold.

Thanks for the help, now on to a more compact muffler. My previous 5th gen had a Two Bros unit which growled like a small block V8 but they are pricey.

Edited October 9, 2018 by DennisA
Photos show the pain of doing twice.