VT750 ACE Camshaft Change

7177 Views 71 Replies 12 Participants Last post by Troy Jollimore, 12 d ago

CSRoad

Discussion Starter · Aug 31, 2019

Due to hot weather baking my shed and family stuff my "two day" project dragged on for a month.
But now it is finally up and running with valve springs and cams from a NT650 Hawk GT.
It now finally feels like a 750 did when I was a kid, it feels like a different engine.

I have not swapped out the exhaust yet, but I'm sure it is a bottleneck in the performance at this point.
I put Uni pods on the carbs, and followed along with stretched and heat treated slide springs to stop the slide flutter and fuel spray that is usually the nightmare of such installations. Slow jets are 42, main jets are 140 front and 145 rear and the Dynojet jet needle is on the second notch. The plugs look OK, but I'm going to have to go richer still with an exhaust change. My rev limiter is set to 6800 rpm that it hits readily in second and third gear, didn't want to cover ground faster than that while sorting it out.

Things I have learned:
I changed the valve springs without pulling the heads, making your own valve spring compressor is a pain, making 3 for different locations is worse.
I would probably pull the heads if I was doing it again even though I had good compression, despite what the manual says it can be done without pulling the engine.
Just for entertainment, stock intake springs you can remove with your thumbs, just grab the keepers with a magnet!

I almost forgot the most important thing: If you use a 4mm wrench when setting your valves tie a couple of feet of string to it. Those things are tiny and if they have a long tail it is harder for them to disappear. "Ah ha I've got you", is way better than "WTF did you go".

NT650 valve covers fit the VT750 although you lose the place for the secondary air cleaner and the crankcase vent is just a hose connection of the rear one and is noisy.
As the bike is now it only takes unplugging the spark plugs and four bolts to remove the covers to check the valve clearances.

I have attached a picture of how it looks with no added trim.

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LAsfinest_SS750

· #21 · 9 mo ago

Also, do you have video of how it runs?

CSRoad

Discussion Starter · #22 · 9 mo ago

This pdf chart shows the 650 Deauville timing.
The inner valve springs are necessary, the rest can be reused if in good shape as they are mostly the same, the spring seats on the 750 ACE are all ready for double springs and I would imagine the 750DC is the same, but better check all the part #'s.
There is no point in changing the cams unless you are willing to spin the engine beyond the factory limit and you need the valve pressure increase to do that and of course the ignition box with the higher limit.

I have no video of my 750 ACE running, but it does run well or at least did 3 weeks ago when I last had it out, it feels like a completely different engine character compared to stock.
Most of my limited riding lately is restricted to short runs on my Versys as I'm trying to break it in and the rest of my traveling seems to be stuck with people in the car. )-;
One of these days I should get a GoPro and rig it up, but it isn't high on my list.

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LAsfinest_SS750

· #23 · 9 mo ago

CSRoad said:
This pdf chart shows the 650 Deauville timing.
The inner valve springs are necessary, the rest can be reused if in good shape as they are mostly the same, the spring seats on the 750 ACE are all ready for double springs and I would imagine the 750DC is the same, but better check all the part #'s.
There is no point in changing the cams unless you are willing to spin the engine beyond the factory limit and you need the valve pressure increase to do that and of course the ignition box with the higher limit.

I have no video of my 750 ACE running, but it does run well or at least did 3 weeks ago when I last had it out, it feels like a completely different engine character compared to stock.
Most of my limited riding lately is restricted to short runs on my Versys as I'm trying to break it in and the rest of my traveling seems to be stuck with people in the car. )-;
One of these days I should get a GoPro and rig it up, but it isn't high on my list.

thank you!

Also, I just did a cross reference, it turns out the valve spring part numbers for VLX 600 are the same.

CSRoad

Discussion Starter · #24 · 9 mo ago

LAsfinest_SS750 said:
Also, I just did a cross reference, it turns out the valve spring part numbers for VLX 600 are the same.

That makes sense the VT600C until 1998 wasn't rev. limited until 8000 rpm, the power was all done at 6500 or so, but Honda let them spin.

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LAsfinest_SS750

· #25 · 9 mo ago

CSRoad said:
That makes sense the VT600C until 1998 wasn't rev. limited until 8000 rpm, the power was all done at 6500 or so, but Honda let them spin.

Welp, I pulled the trigger the UK Deauville camshaft on eBay, $89 total shipped, luckily I have a spare vlx 600 in my garage so I’ll rip the springs from there.

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Froth

· #26 · 9 mo ago

@LAsfinest_SS750 Oh snap, someone else getting into cam profiles and such. Feel free to PM me, I don’t post much but I lurk all the time and I can identify every single RC44 compatible cam by the casting marks on the shaft itself, I’ve always been interested in how the Deauville cams would work in a 750. Been planning on swapping in the pre 99 VLX 600 MR1 cams and springs to replace the Anemic KW0 for a while but life took over hehe.

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LAsfinest_SS750

· #27 · 9 mo ago

Froth said:
@LAsfinest_SS750 Oh snap, someone else getting into cam profiles and such. Feel free to PM me, I don’t post much but I lurk all the time and I can identify every single RC44 compatible cam by the casting marks on the shaft itself, I’ve always been interested in how the Deauville cams would work in a 750. Been planning on swapping in the pre 99 VLX 600 MR1 cams and springs to replace the Anemic KW0 for a while but life took over hehe.

View attachment 304364

Completely understand that.

so used mess with Honda cars and heads were mix and matchable, especially trying to achieve vtec, I’m curious and I wonder if VLX head would mate to VT750, then runs the NT650 cam. Valve cover and head gaskets are cross referenced to fit. The only reason I bring it up is to achieve the use of a single carb. I have a complete 88 VLX 600 and I also have 00 VLX 600 motor sitting which has the single carb.

any thought?

CSRoad

Discussion Starter · #28 · 9 mo ago

There is lots of mixing and matching doable but some may not work easily and most are not worth it when one equates the dollars/time vs. benefit.

The VT600 has an external hard oil line to the top end complete with banjos, where as the 750 uses an internal passage in the cylinder casting.
The rear exhaust port is reduced diameter on the VT600, Honda did this to balance the cylinder flow, I think.
The VT750 has ports the same size and the cylinders are balanced by carb jetting instead.

I'd stay clear of the single carb VT600 heads, I understand they have reduced intake flow as does obviously, the intake manifold and then things are topped off with the KW0
The '99 and later VT600 lost a bunch of power compared with the earlier engines, I think Honda claimed about -2 hp, but the performance figures would indicate a loss of around 7 or 8 hp.

The last year NT650 ('91 only) has internal oiling to the heads and they should/maybe bolt up to the VT 750.
I wanted a pair as my first choice, but could not find any without a bike attached.
I don't know when the Deauville changed to internal oiling, but figure they must have as the Africa Twin and TransAlp made the change.

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zgoldwingman_9185

· #29 · 9 mo ago

CSRoad said:
There is lots of mixing and matching doable but some may not work easily and most are not worth it when one equates the dollars/time vs. benefit.

The VT600 has an external hard oil line to the top end complete with banjos, where as the 750 uses an internal passage in the cylinder casting.
The rear exhaust port is reduced diameter on the VT600, Honda did this to balance the cylinder flow, I think.
The VT750 has ports the same size and the cylinders are balanced by carb jetting instead.

I'd stay clear of the single carb VT600 heads, I understand they have reduced intake flow as does obviously, the intake manifold and then things are topped off with the KW0
The '99 and later VT600 lost a bunch of power compared with the earlier engines, I think Honda claimed about -2 hp, but the performance figures would indicate a loss of around 7 or 8 hp.

The last year NT650 ('91 only) has internal oiling to the heads and they should/maybe bolt up to the VT 750.
I wanted a pair as my first choice, but could not find any without a bike attached.
I don't know when the Deauville changed to internal oiling, but figure they must have as the Africa Twin and TransAlp made the change.

I wanted to go to a single carb on my '05 VT750 Spirit. Purchased a pair of heads from an '06 Aero and swapped out. Found out the Spirit cam rides on 4 journals and the Aero only has three. So had to use the Aero cams. Put a 34mm Mikuni on it, seems to run good. Just finished this job. I hadn't found all this info before I started. It's been interesting.

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CSRoad

Discussion Starter · #30 · 8 mo ago

Not something I would consider, but it might appeal to some folks as there are quite a few that have attempted single carb conversions with varying success and this sounds like a rather clean solution.
Thanks for posting it.

LAsfinest_SS750

· #31 · 8 mo ago

CSRoad said:
Not something I would consider, but it might appeal to some folks as there are quite a few that have attempted single carb conversions with varying success and this sounds like a rather clean solution.
Thanks for posting it.

any helpful pointers for swapping springs and valves?
Camshafts got here from the UK.

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5

CSRoad

Discussion Starter · #32 · 8 mo ago

No real tips, you basically have the choice of pulling the heads and using a C-clamp style valve compressor or doing an overhead valve spring replacement and of course an automotive OH spring compressor won't fit at least not the one I had, likely Snapon has one that will work for $.

The is a video somewhere on the Web that I used for inspiration where the guy replaces valve seals on a Africa Twin or TransAlp with the engine in the frame without removing heads of course the frame is different. Sorry no link for that either.

Anyway I did it without pulling the heads it was a fair McIver hassle and I ended up making three pry-bar type spring compressors, with a bend and a hole to clear the keepers, more or less like a Stanley Wonder bar without the hook made out of 25mm x 8mm bar stock but a bit longer for leverage and they levered off a bracket I made that bolted to the side of the head using two of the fin bolts and caught the pry bar end as a fulcrum with a double nutted eyebolt. II used a flex magnet to scoop the keepers. I could push the intake retainers down with my thumbs originally they were a lot tougher on reassembly with the extra spring.

For the cylinder head I found top dead center backed it up a bit, put 3/16" rope/cord in the plug hole and brought it up again to top dead center to hold the valves closed.
Put shop towels everywhere, plug all holes you don't want valve keepers or other stuff in the crankcase

Follow the procedure in the Service Manual for camshaft removal and timing. I used a long screwdriver to push back the cam chain to loosen the tension on the adjuster and vice grips to hold the wedge. A 2mm bicycle spoke piece works for the locking pin.
Set the valve clearance like usual for the cam.

Now if I was going to do it again I think I'd consider pulling the heads and buying gaskets, it might be easier enough over all to make it worthwhile over the additional costs.
The Service Manual says you need to pull the engine to remove the rear had but you don't, you can double nut and remove the offending cylinder stud for tipping clearance to get it out.

There is other stuff I should remember but it is 3 years ago, I didn't take pics or video and my memory has had better days.
I allowed a weekend to do it, but domestic stuff happened and it took a month 'til completion. )-;

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Gibson86

· #33 · 8 mo ago

Idk pulling the heads and cleaning all the carbon and lapping the valves with some compound and a lapping tool might be worth it. Are the head bolts one time use? Btw I love this posti been keeping up on it and been thinking about a winter project

CSRoad

Discussion Starter · #34 · 8 mo ago

Gibson86 said:
Idk pulling the heads and cleaning all the carbon and lapping the valves with some compound and a lapping tool might be worth it. Are the head bolts one time use? Btw I love this posti been keeping up on it and been thinking about a winter project

Pulling the heads does make sense especially if you have signs of excessive carbon build-up or the compression is a bit low.
The main head bolts are 10mm studs through the cylinder and things are clamped down by nuts they only require lubing and I think something like 35 ft/lbs so not really a lot of stretch and no where like throw away bolts in some cars.

The attached old magazine articles might prove interesting regarding technique, the hop up pieces are long gone of course, as are print mags, but it might be of value none the less.

LAsfinest_SS750

· #35 · 8 mo ago (Edited)

CSRoad said:
No real tips, you basically have the choice of pulling the heads and using a C-clamp style valve compressor or doing an overhead valve spring replacement and of course an automotive OH spring compressor won't fit at least not the one I had, likely Snapon has one that will work for $.

The is a video somewhere on the Web that I used for inspiration where the guy replaces valve seals on a Africa Twin or TransAlp with the engine in the frame without removing heads of course the frame is different. Sorry no link for that either.

Anyway I did it without pulling the heads it was a fair McIver hassle and I ended up making three pry-bar type spring compressors, with a bend and a hole to clear the keepers, more or less like a Stanley Wonder bar without the hook made out of 25mm x 8mm bar stock but a bit longer for leverage and they levered off a bracket I made that bolted to the side of the head using two of the fin bolts and caught the pry bar end as a fulcrum with a double nutted eyebolt. II used a flex magnet to scoop the keepers. I could push the intake retainers down with my thumbs originally they were a lot tougher on reassembly with the extra spring.

For the cylinder head I found top dead center backed it up a bit, put 3/16" rope/cord in the plug hole and brought it up again to top dead center to hold the valves closed.
Put shop towels everywhere, plug all holes you don't want valve keepers or other stuff in the crankcase

Follow the procedure in the Service Manual for camshaft removal and timing. I used a long screwdriver to push back the cam chain to loosen the tension on the adjuster and vice grips to hold the wedge. A 2mm bicycle spoke piece works for the locking pin.
Set the valve clearance like usual for the cam.

Now if I was going to do it again I think I'd consider pulling the heads and buying gaskets, it might be easier enough over all to make it worthwhile over the additional costs.
The Service Manual says you need to pull the engine to remove the rear had but you don't, you can double nut and remove the offending cylinder stud for tipping clearance to get it out.

There is other stuff I should remember but it is 3 years ago, I didn't take pics or video and my memory has had better days.
I allowed a weekend to do it, but domestic stuff happened and it took a month 'til completion. )-;

Lot easier than I thought, I just bolted down the a 10mm wrench to both cam holder bolts.

used It it like a cross bar, then used 21” wrench and leveraging pressure on the 10mm as a cross bar as it puts pressure on the retainer, with help of my son, he used a magnet to pull out the wedge keepers. Took total 10min each side.

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LAsfinest_SS750

· #36 · 8 mo ago

When you did it first time with head on, did you leave the cam on and replaced the shaft?Honestly, no special tool needed I can show how I did it.

LAsfinest_SS750

· #37 · 8 mo ago

Rectangle Font Parallel Circle Pattern

Here are the cross referenced part numbers too.

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CSRoad

Discussion Starter · #38 · 8 mo ago

LAsfinest_SS750 said:
Lot easier than I thought, I just bolted down the a 10mm wrench to both cam holder bolts.

used It it like a cross bar, then used 21” wrench and leveraging pressure on the 10mm as a cross bar as it puts pressure on the retainer, with help of my son it used a magnet to pull out the wedge keepers. Took total 10min each side.

That is thinking outside the box I created myself, thank you it is great what you can learn here.
I made my life far more difficult than it had to be, I think of the time and money I wasted.
Oh well it's not the first and will probably not be the last time. (-:

LAsfinest_SS750

· #39 · 8 mo ago

CSRoad said:
That is thinking outside the box I created myself, thank you it is great what you can learn here.
I made my life far more difficult than it had to be, I think of the time and money I wasted.
Oh well it's not the first and will probably not be the last time. (-:

What about the camshaft? Did you reuse the 750 cams? Or unbolt both bolts form cam gear?

CSRoad

Discussion Starter · #40 · 8 mo ago

No the 750 Cams were put in sandwich bags in a box, never to be reused.
I pulled the gears from the chains before realizing they were the same damn part.
It was all done at one time, I had complete NT650 heads and I dissembled them using a C-clamp valve spring compressor, before diving in.

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