Inside a timing belt tensioner pulley

[Goboy]

When I was installing new Gates T42015 pulleys on my 78, I cut open the old original style pulley to see the insides. Someone may come up with an idea on how to the stock shaft to mount new pulleys. In the photos I have hacksawed the shaft off of the pulley mounting plate. The shaft size is 17.99mm O.D. and15.75 mm in grooves and 25.20mm high.

Original tensioner pulley parts.jpg

tensioner pulley shaft.jpg

[BikeMaine]

Interesting

[Whiskerfish]

https://www.ngwclub.com/File%20Share/TE ... LD-JCS.pdf

[Rednaxs60]

There are a lot of threads on doing this timing belt tensioner bearing mod. Did the mod on my '85 LTD because of age more so than anything else. It was also less expensive than OEM idlers. Cost was $80.00 CDN to do the mod versus $200.00 for OEM idlers.

Here is my rebuild:

Timing Belt Tensioner Rebuild - Just finished this rebuild. I had seen it in this and other forums, and was not going to do it because the idlers didn't feel that bad; however, I'm not one to shirk a challenge. Ordered the idler and it's a Gates T42105. Went to the son-in-law's and cut the idler off and punched out the old stud giving me an opening of approximately 0.54". The opening is countersunk on the back so I surmised that a countersunk head bolt would self-align when tightened up because the new idler would "sit" flush against the base plate. I used a 6 mm hex drive and 17 mm socket.

This picture shows the parts used with the old idler as well. You will notice that the bolt, 10 mm by 25 mm, has a flat countersunk head that should self-align when tightened.

Old and new parts.jpg

This picture shows the countersunk hole on the back of the base plate that the bolt will fit into.

Base Plate countersink.jpg

This picture shows the new idler installed and the new bolt "proud" of the base plate.

New idler installed on base plate.jpg

This picture shows the tensioner with the new bolt flush with the back of the base plate. I used a 24 tooth hacksaw blade to trim off the excess bolt head so it is flush with the base plate. The hex hole is still 1/8th inch deep so I will be able to replace later on if necessary.

Bolt trimmed to base plate - 1.jpg

Bolt trimmed to base plate - 2.jpg

On to post #2

[Rednaxs60]

Post #2.

This picture shows the front of the tensioner.

Tensioner with new idler installed.jpg

This picture shows the finished tensioners.

Finished new timing belt tensioners.jpg

I was pleasantly surprised how easy this modification is to do with minimum tools. Items:

hacksaw
Punch/chisel - to remove old stud after hacksaw used to remove old idler
17 mm socket
6 mm hex drive
10 mm by 25 mm flat countersunk bolt
nylock nut with flat washer
Gates 42105 idler

Total cost for this mod is approximately $90.00. I did not need to use a 1/2 inch drill bit that I bought specifically for this, so the resulting would have been $84.00, significantly less than 2 new timing belt tensioners from mother Honda.

Cheers

[5speed]

Rednaxs60..do you have any concerns that cutting the remaining head off the bolt weakened it in regards to side tension on the bolt?
It looks like the plate is thick enough to allow a deeper counter sink for the bolt.

[Whiskerfish]

There is actually some room behind the plate for a thin bolt head. I used Bolts and ground them down some but no where near flush.

[Rednaxs60]

Rednaxs60..do you have any concerns that cutting the remaining head off the bolt weakened it in regards to side tension on the bolt?
It looks like the plate is thick enough to allow a deeper counter sink for the bolt.

Not at all. There is still a lot of meat on the bolt head and the countersink is a lot as well. There should be little if any side loading on the bolt once it is tightened/torqued. The bearing sits flat against the mounting plate so there has to be a lot of stress from the timing belt to do any side loading. Timing belts aren't supposed to be that tight. Had mine in for 15,000 Kms and no issues to date.

I used nylock nuts so that in the future, if I had to replace the bearings it would be an easy exchange.

Cheers

[5speed]

tks for the response. I will be doing this upgrade in the near future.

[Rednaxs60]

When you do this mod and cut off the old pulley with a hacksaw (faster and cleaner than using an angle grinder), punch out all of the old bolt that held the old pulley on. Will give the same look as in my picture in my previous post.

Cheers

[Track T 2411]

This certainly looks easy, I don't know where I got the idea that it was really involved and needed special tools... I might just give it a go for the sake of peace of mind.

[Goboy]

On my 78 I ground about half of the head flush (there's a small step on the head) to insure that when the spring applies tension toward the bolt there won't be interference. You could also grind a little off that dog leg bracket or a combination of the two. I can just get the new belts on without too much trouble. It was much easier than my first time, practice helps!

Idler pulley mount plate back view 02.jpg

Photo of them installed on the bike. The hose is so I can warm up the bike and readjust the belt tension while the bike is warmed up. The engine can expand enough to make the belts too tight, so bring it up to operating temp and see if you feel a difference in the belt tension. One other thing I found while warming up the engine I noticed the rt. timing sprocket was wobbling, turned out to be a bent sprocket, put another used one on now its fine. Lucky! as I was worried it was the cam snout. The bike had been down at some time in the past, as the bottom of the right crash bar was ground flat. I also found that the cover plate behind the sprocket was bent and had cracks and the rt radiator wing has been repainted.

Idler pulleys and hose.jpg

[Beetleman]

I did this same mod when I changed my head gaskets. I used a port-a-band saw at work to cut the original studs off.
I got the old stud out by centering the stud over a size 18 socket. I then took a smaller socket that was slightly smaller than the stud size and used it like a punch on the other side and the stud head popped out pretty easily.
The gates rollers look like they're made out of better materials than the stamped steel originals. I would hope that they will last quite a bit longer than the originals.

[robin1731]

snip................ I would hope that they will last quite a bit longer than the originals.

I don't know. 40 years is a long time.

.

[dartman1962]

Hi, I was just reading your post. you mention the Gates P#42015 first then down in your other comments you
mention the P#42105. So is the P#42015 or 42105?
Thanks Dartman.