All four slides labeled IOM and all four slides dated July 1971... 
any info much obliged!

1.



2.



3.



4.



regards

I THINK 1&3 looks like the hairpin exit at Mallory park.
2. Signpost corner?
4. ballagh bridge?

my hazy memory tells me Pic 1 & 3 is Mallory Hairpin with the white boards on inside, Pic 2 methinks is Creg ny Baa, I used to live up by Signpost don't recall ever seeing the road marked like that at Signpost, Pic 4 Ballaugh Bridge .... sorry - riders, bikes. outfits are a little before my "time" .. really good to see these fab pics and collective history, info, knowledge.

1 & 3 are definitely Mallory Park on the hairpin exit. 2 would be Creg Ny Baa and obviously Ballaugh for 4. Pic 4 would be the 750cc sidecar race as denoted by the black plates and it looks like there's a BSA sticker on the fairing. I wonder if it's Peter Sheridan & Philip Smith, both sadly lost in an awful accident at Oulton in 1971. My dad gave them a tow back to the paddock after they broke down in practice and if I remember right, they had a white outfit. They were entered on a BSA in the 1970 750 sidecar TT. Pic 2 is a 500cc outfit (yellow plates) and looking at the colour scheme, I'm thinking it might be the Woodhouse brothers. All this is just guesswork on my part!

I've put a link to this thread on Steve's Place where all the sidecar guys hang out, so maybe we can get a positive ID.

Pic 2, yep, looking at it now definitely the creg.
Thinking about it, I don't think Signpost corner ever had road markings like that...but of course I could be wrong... again!!

Some info courtesy of Steve's Place:
Pic 1: Bill & Mike Crook - Unity BSA

Pic 2: The number 25 outfit is Eric Parkinson / Roger Osbourne (assuming the shot is from 1971) on a 500cc Crescent

I'll keep checking the other thread and report back!

Not sure,but I don't think that's the Crescent 2 stroke,Sticky.Seem to remember it was water cooled which the one in the pic doesn't appear to be.

Yes, I can confirm that the Crescent outboard engine, that was used in some motorbikes, was water cooled. I worked in the firm that constructed it. It was a three cylinders two stroke 500cc. There were two models for motorboat racing. One on gasoline and one on methanol for the classes CS and C. The Swede A V Andersson raced his Crescent solo bike in the Senior TT 1969 and he was a DNF.